perf symbol: Add LoongArch case in get_plt_sizes()

We can see the following definitions in bfd/elfnn-loongarch.c:

  #define PLT_HEADER_INSNS 8
  #define PLT_HEADER_SIZE (PLT_HEADER_INSNS * 4)

  #define PLT_ENTRY_INSNS 4
  #define PLT_ENTRY_SIZE (PLT_ENTRY_INSNS * 4)

so plt header size is 32 and plt entry size is 16 on LoongArch,
let us add LoongArch case in get_plt_sizes().

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Acked-by: Huacai Chen <chenhuacai@loongson.cn>
Reviewed-by: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: loongarch@lists.linux.dev
Cc: loongson-kernel@lists.loongnix.cn
Cc: Ingo Molnar <mingo@redhat.com>
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=bfd/elfnn-loongarch.c
Link: https://lore.kernel.org/r/1684835873-15956-1-git-send-email-yangtiezhu@loongson.cn
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

tools/perf/util/symbol-elf.c

@@ -42,6 +42,10 @@
 #define EM_AARCH64	183  /* ARM 64 bit */
 #endif
 
+#ifndef EM_LOONGARCH
+#define EM_LOONGARCH	258
+#endif
+
 #ifndef ELF32_ST_VISIBILITY
 #define ELF32_ST_VISIBILITY(o)	((o) & 0x03)
 #endif
@@ -438,6 +442,10 @@ static bool get_plt_sizes(struct dso *dso, GElf_Ehdr *ehdr, GElf_Shdr *shdr_plt,
 		*plt_header_size = 32;
 		*plt_entry_size = 16;
 		return true;
+	case EM_LOONGARCH:
+		*plt_header_size = 32;
+		*plt_entry_size = 16;
+		return true;
 	case EM_SPARC:
 		*plt_header_size = 48;
 		*plt_entry_size = 12;