Add a dquot id field to the incore dquot, and use that instead of the
one in qcore.  This eliminates a bunch of endian conversions and will
eventually allow us to remove qcore entirely.

We also rearrange the start of xfs_dquot to remove padding holes, saving
8 bytes.
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NChandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NAllison Collins <allison.henderson@oracle.com>