xfs: stop using q_core warning counters in the quota code

Add warning counter fields to the incore dquot, and use that instead of
the ones in qcore.  This eliminates a bunch of endian conversions and
will eventually allow us to remove qcore entirely.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Allison Collins <allison.henderson@oracle.com>