Fix the Mares usb-serial communication

The BLE changes in commit e83732e are
causing major problems for some of the usb-serial enabled models, like
the Puck Pro and Quad Air.

These models appear to require a small delay of a few milliseconds
between sending the two command bytes and the remainder of the command
payload. I suspect the device is still busy processing those first two
bytes, and thus not ready in time to receive the remaining data. Instead
of manually adding a fixed delay, restore the previous behaviour and
wait for the ack byte again. This has the advantage that the delay is
automatically proportional to the response time of the dive computer.

For the BLE communication nothing changes.

src/mares_iconhd.c

@@ -183,6 +183,7 @@ mares_iconhd_packet (mares_iconhd_device_t *device,
 {
 	dc_status_t status = DC_STATUS_SUCCESS;
 	dc_device_t *abstract = (dc_device_t *) device;
+	dc_transport_t transport = dc_iostream_get_transport (device->iostream);
 
 	if (device_is_cancelled (abstract))
 		return DC_STATUS_CANCELLED;
@@ -198,7 +199,7 @@ mares_iconhd_packet (mares_iconhd_device_t *device,
 	}
 
 	// Send the command payload to the dive computer.
-	if (size) {
+	if (size && transport == DC_TRANSPORT_BLE) {
 		status = dc_iostream_write (device->iostream, data, size, NULL);
 		if (status != DC_STATUS_SUCCESS) {
 			ERROR (abstract->context, "Failed to send the command.");
@@ -220,6 +221,15 @@ mares_iconhd_packet (mares_iconhd_device_t *device,
 		return DC_STATUS_PROTOCOL;
 	}
 
+	// Send the command payload to the dive computer.
+	if (size && transport != DC_TRANSPORT_BLE) {
+		status = dc_iostream_write (device->iostream, data, size, NULL);
+		if (status != DC_STATUS_SUCCESS) {
+			ERROR (abstract->context, "Failed to send the command data.");
+			return status;
+		}
+	}
+
 	// Read the packet.
 	status = dc_iostream_read (device->iostream, answer, asize, NULL);
 	if (status != DC_STATUS_SUCCESS) {