audit: less stack usage for /proc/*/loginuid

%u requires 10 characters at most not 20.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

fs/proc/base.c

@@ -1228,7 +1228,7 @@ static const struct file_operations proc_oom_score_adj_operations = {
 };
 
 #ifdef CONFIG_AUDITSYSCALL
-#define TMPBUFLEN 21
+#define TMPBUFLEN 11
 static ssize_t proc_loginuid_read(struct file * file, char __user * buf,
 				  size_t count, loff_t *ppos)
 {