xfs: use bitops interface for buf log item AIL flag check

The xfs_log_item flags were converted to atomic bitops as of commit
22525c17 ("xfs: log item flags are racy"). The assert check for
AIL presence in xfs_buf_item_relse() still uses the old value based
check. This likely went unnoticed as XFS_LI_IN_AIL evaluates to 0
and causes the assert to unconditionally pass. Fix up the check.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Fixes: 22525c17 ("xfs: log item flags are racy")
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>