xfs: remove warning counters from struct xfs_dquot_res

xfs: remove warning counters from struct xfs_dquot_res

Source kernel commit: 2e06df552a7cba13eb0046b9116a9aa26001ee2c

Warning counts are not used anywhere in the kernel. In addition, there
are no use cases, test coverage, or documentation for this functionality.
Remove the 'warnings' field from struct xfs_dquot_res and any other
related code.

Signed-off-by: Catherine Hoang <catherine.hoang@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>