xfs: pass explicit mount pointer to rtalloc query functions

Pass an explicit xfs_mount pointer to the rtalloc query functions so
that they can support transactionless queries.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>