usb: gadget: ci13xxx: Move EP and DMA buffer init to udc_probe

EP and dma pool allocation happens in udc_start. But, now
composite_bind is called (which calls usb_ep_alloc_request) before
udc_start from udc-core.
Hence, move initialization code from udc_start to udc_probe.

Change-Id: Ibfc710f856d982b2ce66626dc8d5556a23520a0e
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>