usb: f_rmnet: Add function suspend/resume for super-speed wakeup

USB super-speed mode mode requires device to advertise remote
wakeup capability at function driver level called as function
wakeup capability. Host queries this using get_status and
uses set_feature to enable function remote wakeup before
initiating function suspend. This is also required to initiate
remote wakeup as well which is otherwise failed by UDC in SS mode.

CRs-fixed: 2027141
Change-Id: I337de8b66299db08d4af967b858677f3b7c2a04d
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>