dfu:ext4:fix Fix ext4{read|write} command formatting

In the following commit:
"dfu: Support larger than memory transfers."
SHA1: ea2453d56b

The ext4{read|write} command formatting has been changed. It removed
a write mandatory [sizebytes] parameter.

It extents DFU_FS_EXT4 case at mmc_file_op to provide mandatory
parameter for DFU write.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Cc: Tom Rini <trini@ti.com>
Cc: Pantelis Antoniou <panto@antoniou-consulting.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Heiko Schocher <hs@denx.de>

drivers/dfu/dfu_mmc.c

@@ -98,6 +98,8 @@ static int mmc_file_op(enum dfu_mmc_op op, struct dfu_entity *dfu,
 			op == DFU_OP_READ ? "load" : "write",
 			dfu->data.mmc.dev, dfu->data.mmc.part,
 			(unsigned int) buf, dfu->name);
+		if (op == DFU_OP_WRITE)
+			sprintf(cmd_buf + strlen(cmd_buf), " %ld", *len);
 		break;
 	default:
 		printf("%s: Layout (%s) not (yet) supported!\n", __func__,