xfs: don't set quota warning values

Having just dropped support for quota warning limits and warning
counters, the warning fields no longer have any meaning. Prevent these
fields from being set by removing QC_WARNS_MASK from XFS_QC_SETINFO_MASK
and XFS_QC_MASK.

Signed-off-by: Catherine Hoang <catherine.hoang@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>