libata-scsi: do not respond with "invalid field" for FORMAT UNIT

It does not make sense and is confusing to respond with "Invalid
field in CDB" while we have no support at all implemented for
FORMAT UNIT. It is decent to let it go to the default, which
will respond with "Invalid command operation code" instead.
Signed-off-by: NTom Yan <tom.ty89@gmail.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

drivers/ata/libata-scsi.c

@@ -4039,11 +4039,6 @@ void ata_scsi_simulate(struct ata_device *dev, struct scsi_cmnd *cmd)
 	args.done = cmd->scsi_done;
 
 	switch(scsicmd[0]) {
-	/* TODO: worth improving? */
-	case FORMAT_UNIT:
-		ata_scsi_invalid_field(dev, cmd, 0);
-		break;
-
 	case INQUIRY:
 		if (scsicmd[1] & 2)		   /* is CmdDt set?  */
 		    ata_scsi_invalid_field(dev, cmd, 1);