xfs: xlog_write() no longer needs contwr state

The rework of xlog_write() no longer requires xlog_get_iclog_state()
to tell it about internal iclog space reservation state to direct it
on what to do. Remove this parameter.

$ size fs/xfs/xfs_log.o.*
   text	   data	    bss	    dec	    hex	filename
  26520	    560	      8	  27088	   69d0	fs/xfs/xfs_log.o.orig
  26384	    560	      8	  26952	   6948	fs/xfs/xfs_log.o.patched

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>