usb: gadget: f_rndis: Add 'wceis' flag to indicate 'Wireless' RNDIS

The 'wceis' flag used to indicate the device as wireless controller.
Set the default value is true as this is what we want in most of the
cases.

Change-Id: Idc03717526350421d94b9445333b36823a372aad
Signed-off-by: Liangliang Lu <luliang@codeaurora.org>