s390/uapi: cover statfs padding by growing f_spare

s390/uapi: cover statfs padding by growing f_spare

pahole says:

	struct compat_statfs64 {
		...
		u32			f_spare[4];		/*    68    16 */
		/* size: 88, cachelines: 1, members: 12 */
		/* padding: 4 */

	struct statfs {
		...
		unsigned int		f_spare[4];		/*    68    16 */
		/* size: 88, cachelines: 1, members: 12 */
		/* padding: 4 */

	struct statfs64 {
		...
		unsigned int		f_spare[4];		/*    68    16 */
		/* size: 88, cachelines: 1, members: 12 */
		/* padding: 4 */

One has to keep the existence of padding in mind when working with
these structs. Grow f_spare arrays to 5 in order to simplify things.

Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20230504144021.808932-3-iii@linux.ibm.com
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>