mips: add asm/syscalls.h header

System call prototypes are generally in linux/syscalls.h, but there are a
couple of mips specific entry points that are missing there:

arch/mips/kernel/signal.c:636:17: error: no previous prototype for 'sys_sigreturn' [-Werror=missing-prototypes]
arch/mips/kernel/signal.c:673:17: error: no previous prototype for 'sys_rt_sigreturn' [-Werror=missing-prototypes]
arch/mips/kernel/syscall.c:51:16: error: no previous prototype for 'sysm_pipe' [-Werror=missing-prototypes]
arch/mips/kernel/mips-mt-fpaff.c:65:17: error: no previous prototype for 'mipsmt_sys_sched_setaffinity' [-Werror=missing-prototypes]
arch/mips/kernel/mips-mt-fpaff.c:157:17: error: no previous prototype for 'mipsmt_sys_sched_getaffinity' [-Werror=missing-prototypes]

Add these to a new asm/syscalls.h as we have in other architectures.

Link: https://lkml.kernel.org/r/20231204115710.2247097-3-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Stephen Rothwell <sfr@rothwell.id.au>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/mips/include/asm/syscalls.h

@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _ASM_MIPS_SYSCALLS_H
+#define _ASM_MIPS_SYSCALLS_H
+
+#include <linux/linkage.h>
+#include <linux/compat.h>
+
+asmlinkage void sys_sigreturn(void);
+asmlinkage void sys_rt_sigreturn(void);
+asmlinkage int sysm_pipe(void);
+asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len,
+                                     unsigned long __user *user_mask_ptr);
+asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
+                                     unsigned long __user *user_mask_ptr);
+asmlinkage long sys32_fallocate(int fd, int mode, unsigned offset_a2,
+				unsigned offset_a3, unsigned len_a4,
+				unsigned len_a5);
+asmlinkage long sys32_fadvise64_64(int fd, int __pad,
+				   unsigned long a2, unsigned long a3,
+				   unsigned long a4, unsigned long a5,
+				   int flags);
+asmlinkage ssize_t sys32_readahead(int fd, u32 pad0, u64 a2, u64 a3,
+				   size_t count);
+asmlinkage long sys32_sync_file_range(int fd, int __pad,
+				      unsigned long a2, unsigned long a3,
+				      unsigned long a4, unsigned long a5,
+				      int flags);
+asmlinkage void sys32_rt_sigreturn(void);
+asmlinkage void sys32_sigreturn(void);
+asmlinkage int sys32_sigsuspend(compat_sigset_t __user *uset);
+asmlinkage void sysn32_rt_sigreturn(void);
+
+#endif

arch/mips/kernel/linux32.c

@@ -42,6 +42,7 @@
 #include <linux/uaccess.h>
 #include <asm/mmu_context.h>
 #include <asm/mman.h>
+#include <asm/syscalls.h>
 
 #ifdef __MIPSEB__
 #define merge_64(r1, r2) ((((r1) & 0xffffffffUL) << 32) + ((r2) & 0xffffffffUL))

arch/mips/kernel/mips-mt-fpaff.c

@@ -15,6 +15,7 @@
 #include <linux/security.h>
 #include <linux/types.h>
 #include <linux/uaccess.h>
+#include <asm/syscalls.h>
 
 /*
  * CPU mask used to set process affinity for MT VPEs/TCs with FPUs

arch/mips/kernel/signal.c

@@ -38,6 +38,7 @@
 #include <asm/dsp.h>
 #include <asm/inst.h>
 #include <asm/msa.h>
+#include <asm/syscalls.h>
 
 #include "signal-common.h"
 

arch/mips/kernel/signal32.c

@@ -18,6 +18,7 @@
 #include <asm/compat-signal.h>
 #include <linux/uaccess.h>
 #include <asm/unistd.h>
+#include <asm/syscalls.h>
 
 #include "signal-common.h"
 

arch/mips/kernel/signal_n32.c

@@ -24,6 +24,7 @@
 #include <asm/ucontext.h>
 #include <asm/fpu.h>
 #include <asm/cpu-features.h>
+#include <asm/syscalls.h>
 
 #include "signal-common.h"
 

arch/mips/kernel/signal_o32.c

@@ -19,6 +19,7 @@
 #include <asm/dsp.h>
 #include <asm/sim.h>
 #include <asm/unistd.h>
+#include <asm/syscalls.h>
 
 #include "signal-common.h"
 

arch/mips/kernel/syscall.c

@@ -39,6 +39,7 @@
 #include <asm/shmparam.h>
 #include <asm/sync.h>
 #include <asm/sysmips.h>
+#include <asm/syscalls.h>
 #include <asm/switch_to.h>
 
 /*