xfs: fix u32 type usage in sb validation function

Source kernel commit: 131fa58d391fc0939f6c66b23776ad5df5db20f9

Don't use u32, use uint32_t, because this won't work in xfsprogs.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
[sandeen: no-op commit, fixed previously to keep build working]
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>