ethernet: Make it possible for ethernet drivers to send/receive net_buffers.

This paves the way for a variety of more interesting interactions
between drivers and the stack which are currently not possible
(e.g. checksum offload, #18744). The main advantage for the moment
is that we will save a memcpy of the buffer on each send/receive.

Adapt the virtio_net driver so that at least one driver is using
the new interface. Network still seems to work OK with it.

Change-Id: Ic5832e4865e3e1bed7462583ca1ffd16418d7cab
Reviewed-on: https://review.haiku-os.org/c/haiku/+/7912
Reviewed-by: waddlesplash <[email protected]>

headers/private/net/ether_driver.h

@@ -23,8 +23,11 @@ enum {
 	ETHER_GETFRAMESIZE,						/* get frame size (required) (int *) */
 	ETHER_SET_LINK_STATE_SEM,
 		/* pass over a semaphore to release on link state changes (sem_id *) */
-	ETHER_GET_LINK_STATE
+	ETHER_GET_LINK_STATE,
 		/* get line speed, quality, duplex mode, etc. (ether_link_state_t *) */
+
+	ETHER_SEND_NET_BUFFER,					/* send a net_buffer */
+	ETHER_RECEIVE_NET_BUFFER,				/* receive a net_buffer */
 };