The only external caller of xfs_inode_walk* happens in quotaoff, when we
want to walk all the incore inodes to detach the dquots.  Move this code
to xfs_icache.c so that we can hide xfs_inode_walk as the starting step
in more cleanups of inode walks.
Signed-off-by: NDarrick J. Wong <djwong@kernel.org>
Reviewed-by: NDave Chinner <dchinner@redhat.com>