xfs: remove xfs_qm_vop_chown_reserve

Now that the only caller of this function is xfs_trans_alloc_ichange,
just open-code the meat of _chown_reserve in that caller.  Drop the
(redundant) [ugp]id checks because xfs has a 1:1 relationship between
quota ids and incore dquots.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>