scsi: megaraid: megaraid_sas_base: Mark expected switch fall-through

In preparation to enabling -Wimplicit-fallthrough, mark switch cases where
we are expecting to fall through.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/megaraid/megaraid_sas_base.c

@@ -3281,6 +3281,7 @@ megasas_complete_cmd(struct megasas_instance *instance, struct megasas_cmd *cmd,
 			megasas_complete_int_cmd(instance, cmd);
 			break;
 		}
+		/* fall through */
 
 	case MFI_CMD_LD_READ:
 	case MFI_CMD_LD_WRITE: