net: usbnet: Add support for IPA s/w bridge

Add support to bypass linux network stack and pass
IPv4 and IPv6 packets directly to IPA using a s/w bridge.

This helps avoid context switches due to packet processing
in soft IRQ context thereby freeing CPU and improving
thoughput.

Change-Id: I91530d0b27c7dcaba81d7a5e4ca72c22b2917c70
Signed-off-by: Devdutt Patnaik <dpatnaik@codeaurora.org>
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>