usb: gadget: add u_qc_ether - QC Ethernet-over-USB link layer utilities.

This utilities is based on Ethernet-over-USB link layer utilities and
contains QC specific implementation (using SPS BAM-to-BAM for data
channel).

Change-Id: Iec417b4df57c34d1ba9368495c7a489c36ddf6dc
Signed-off-by: Ofir Cohen <ofirc@codeaurora.org>