Btrfs: remove redundant check in rbio_can_merge

Given the above
'
if (last->operation != cur->operation)
	return 0;
',
it's guaranteed that two operations are same.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/raid56.c

@@ -594,12 +594,10 @@ static int rbio_can_merge(struct btrfs_raid_bio *last,
 	 * bio list here, anyone else that wants to
 	 * change this stripe needs to do their own rmw.
 	 */
-	if (last->operation == BTRFS_RBIO_PARITY_SCRUB ||
-	    cur->operation == BTRFS_RBIO_PARITY_SCRUB)
+	if (last->operation == BTRFS_RBIO_PARITY_SCRUB)
 		return 0;
 
-	if (last->operation == BTRFS_RBIO_REBUILD_MISSING ||
-	    cur->operation == BTRFS_RBIO_REBUILD_MISSING)
+	if (last->operation == BTRFS_RBIO_REBUILD_MISSING)
 		return 0;
 
 	return 1;