s390/uapi: fix struct statfs64 definition

With b8668fd0 "s390/uapi: change struct statfs[64] member types
to unsigned values" the size of a couple of struct statfs64 member got
incorrectly changed from 64 to 32 bit for 32 bit builds.

Fix this by changing the type of couple of struct statfs64 members from
unsigned long to unsigned long long.
The definition of struct compat_statfs64 was correct however.

Cc: stable@vger.kernel.org # v3.10+
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>