perf tools: fix type mismatch - long vs __statfs_word

From "include/uapi/asm-generic/statfs.h" it is seen that "statfs.f_type" is of
type "__statfs_word" which in its turn is "__u32" (unsigned int) for 32-bit
systems.

So in case of compilation with "-Werror" following breakage happens:
--->---
fs.c: In function ‘fs__valid_mount’:
fs.c:76:24: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
  else if (st_fs.f_type != magic)
                        ^
cc1: all warnings being treated as errors
--->---

Note that now when fs.c is in "lib/api/fs" and in "tools/lib/api/Makefile"
CFLAGS has hard-coded "-Werror" this is inevitable even if obe builds "perf"
with "WERROR=0".

Signed-off-by: Alexey Brodkin <[email protected]>

Cc: Vineet Gupta <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Jiri Olsa <[email protected]>

Author: abrodkin

tools/lib/api/fs/fs.c

@@ -73,7 +73,7 @@ static int fs__valid_mount(const char *fs, long magic)
 
 	if (statfs(fs, &st_fs) < 0)
 		return -ENOENT;
-	else if (st_fs.f_type != magic)
+	else if ((long)st_fs.f_type != magic)
 		return -ENOENT;
 
 	return 0;