perf: Fix a build error with some GCC versions

Fix this:

 util/cgroup.c: In function ‘open_cgroup’:
 util/cgroup.c:16:16: error: ‘saved_ptr’ may be used uninitialized in this function
 util/cgroup.c:16:16: note: ‘saved_ptr’ was declared here

Apparently newer GCC (4.6) can figure out that this variable is properly
initialized - but some versions of GCC (such as 4.5.2) need help.
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

tools/perf/util/cgroup.c

@@ -13,7 +13,7 @@ cgroupfs_find_mountpoint(char *buf, size_t maxlen)
 {
 	FILE *fp;
 	char mountpoint[MAX_PATH+1], tokens[MAX_PATH+1], type[MAX_PATH+1];
-	char *token, *saved_ptr;
+	char *token, *saved_ptr = NULL;
 	int found = 0;
 
 	fp = fopen("/proc/mounts", "r");