block: get rid of bio_rw and READA

These two are confusing leftover of the old world order, combining
values of the REQ_OP_ and REQ_ namespaces.  For callers that don't
special case we mostly just replace bi_rw with bio_data_dir or
op_is_write, except for the few cases where a switch over the REQ_OP_
values makes more sense.  Any check for READA is replaced with an
explicit check for REQ_RAHEAD.  Also remove the READA alias for
REQ_RAHEAD.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/lightnvm/rrpc.c b/drivers/lightnvm/rrpc.c
index fa1ab04..37fcaad 100644
--- a/drivers/lightnvm/rrpc.c
+++ b/drivers/lightnvm/rrpc.c
@@ -853,14 +853,14 @@
 			return NVM_IO_ERR;
 		}
 
-		if (bio_rw(bio) == WRITE)
+		if (bio_op(bio) == REQ_OP_WRITE)
 			return rrpc_write_ppalist_rq(rrpc, bio, rqd, flags,
 									npages);
 
 		return rrpc_read_ppalist_rq(rrpc, bio, rqd, flags, npages);
 	}
 
-	if (bio_rw(bio) == WRITE)
+	if (bio_op(bio) == REQ_OP_WRITE)
 		return rrpc_write_rq(rrpc, bio, rqd, flags);
 
 	return rrpc_read_rq(rrpc, bio, rqd, flags);