WIP: LInux Networking support via USB

[Fishwaldo]

this setups networking between Linux running on D0, and this firmware running on M0. It also setups a RNDIS adapter on USB to communicate with a external host.

The firmware on M0 acts as a Network Bridge, forwarding packets between a rpmsg-net based adapter, the USB rndis adapter and the local firmware.

Currently hardcoded to use 192.168.5.x/24 network range. The IP address of your PC should be 192.168.5.1 and if you want networking, you need to enable NAT on your host.

This currently requires a few patches to bl_mcu_sdk LWIP component to fix bugs or workarounds

• Ping Reply Packets are copied from Ping Request Packet, including the inbound interface index. This confuses the bridge code when sending the reply back out.
• Bridge Code thinks all interfaces are "local" interface. (BR0 in the code) and wont forward ARP requests to the other interfaces
• Bridge Code submits packets to the TCP/IP task from a interrupt handler using unsafe xQueueSend (instead of xQueueSendFromISR) when called from a interrupt context. Currently, both USB and rpmsg-net RX handling is in interupts