usb: f_gsi: Add ethernet as extended protocol for rmnet and dpl

For some targets rmnet and DPL data path goes over ethernet device.
Treat such rmnet and DPL as extended protocols and pass instance name
as gsi.function_name.extended_prot_name. Extended protocol id is used
to perform ethernet device specific operations for data path. Define
and use usb_prot_id enum which includes IPA accelerated protocol ids
as well as extended non-accelerated protocol ids. Create new control
device node for rmnet and DPL extended protocol instances.

Change-Id: I1a0a04151d83e1cddf49aa2254e4ea862e2504d8
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>