xfs: remove use of do_div with 32-bit dividend in quota
The kbuild test robot caught this; in debug code we have another
caller of do_div with a 32-bit dividend (j) which is caught now
that we are using the kernel-supplied do_div.
None of the values used here are 64-bit; just use simple division.
Signed-off-by: Eric Sandeen <sandeen@redhat.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>