Flags passed to Q_XQUOTARM were not sanity checked for invalid values.
Fix that.

Fixes: 9da93f9b ("xfs: fix Q_XQUOTARM ioctl")
Reported-by: NYang Xu <xuyang2018.jy@cn.fujitsu.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Reviewed-by: NEric Sandeen <sandeen@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>