usb: gadget: Add snapshot of USB GSI function driver

This change adds USB GSI function driver which provides USB RMNET/RNDIS/
ECM/MBIM/DPL related functionalities with GSI hardware accelerated path.
This snapshot is taken as of msm-4.14 commit <ceb432de347d> ("Merge "perf:
Add workaround for performance monitor irq burst"").

Change-Id: If849fdeab445e99dc914060eae98e1948a48e3d2
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>