usb: gadget: Add flag to determine gadget controller

Add a flag is_chipidea to determine whether the USB device
controller is ChipIdea or not. Set the flag to true during
CI UDC probe.

Change-Id: I8d36e4a1ae8e95723e1ef90ca694488926e78bc0
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>