xfs: Refactor xfs_da_state_alloc() helper

Every call to xfs_da_state_alloc() also requires setting up state->args
and state->mp

Change xfs_da_state_alloc() to receive an xfs_da_args_t as argument and
return a xfs_da_state_t with both args and mp already set.

Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
[darrick: reduce struct typedef usage]
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>