xfs: always use xfs_dquot_type when extracting type from a dquot

Always use the xfs_dquot_type helper to extract the quota type from an
incore dquot.  This moves responsibility for filtering internal state
information and whatnot to anybody passing around a struct xfs_dquot.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>