XFS: Use a signed return type for suffix_kstrtoint()

The return type "unsigned long" was used by the suffix_kstrtoint()
function even though it will eventually return a negative error code.
Improve this implementation detail by using the type "int" instead.

This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_super.c

@@ -137,7 +137,7 @@ static const match_table_t tokens = {
 };
 
 
-STATIC unsigned long
+STATIC int
 suffix_kstrtoint(char *s, unsigned int base, int *res)
 {
 	int	last, shift_left_factor = 0, _res;