perf beauty mmap_flags: Fix script for archs that use the generic mman.h

To address this error:

  grep: /root/linux-next/tools/arch/xxxxx/include/uapi/asm//mman.h:
  No such file or directory

Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Acked-by: Huacai Chen <chenhuacai@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: loongarch@lists.linux.dev
Cc: loongson-kernel@lists.loongnix.cn
Link: https://lore.kernel.org/r/42e8e3565d6035302907426c1e65483b2a4007f5.1692962043.git.siyanteng@loongson.cn
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: Yanteng Si

tools/perf/trace/beauty/mmap_flags.sh

@@ -19,7 +19,7 @@ arch_mman=${arch_header_dir}/mman.h
 
 printf "static const char *mmap_flags[] = {\n"
 regex='^[[:space:]]*#[[:space:]]*define[[:space:]]+MAP_([[:alnum:]_]+)[[:space:]]+(0x[[:xdigit:]]+)[[:space:]]*.*'
-grep -E -q $regex ${arch_mman} && \
+([ -f ${arch_mman} ] && grep -E -q $regex ${arch_mman}) && \
 (grep -E $regex ${arch_mman} | \
 	sed -r "s/$regex/\2 \1 \1 \1 \2/g"	| \
 	xargs printf "\t[ilog2(%s) + 1] = \"%s\",\n#ifndef MAP_%s\n#define MAP_%s %s\n#endif\n")