RISC-V: stacktrace: Declare sp_in_global outside ifdef

riscv:allnoconfig and riscv:tinyconfig fail to compile.

arch/riscv/kernel/stacktrace.c: In function 'walk_stackframe':
arch/riscv/kernel/stacktrace.c:78:8: error: 'sp_in_global' undeclared

sp_in_global is declared inside CONFIG_FRAME_POINTER but used outside
of it.

Fixes: 52e7c52d2d ("RISC-V: Stop relying on GCC's register allocator's hueristics")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/kernel/stacktrace.c

@@ -12,6 +12,8 @@
 #include <linux/stacktrace.h>
 #include <linux/ftrace.h>
 
+register unsigned long sp_in_global __asm__("sp");
+
 #ifdef CONFIG_FRAME_POINTER
 
 struct stackframe {
@@ -19,8 +21,6 @@ struct stackframe {
 	unsigned long ra;
 };
 
-register unsigned long sp_in_global __asm__("sp");
-
 void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
 			     bool (*fn)(unsigned long, void *), void *arg)
 {