usb: gadget: ci13xxx_udc: init ep_list head for each ep at probe

If the lists are not init properly this causes a crash when stopping udc,
since stop function calls list_emtpy function on them.

Change-Id: Ibd9f7daddcc991c0efeb324748e852c86f76c423
Signed-off-by: Lena Salman <esalman@codeaurora.org>