usb: gadget: Initialize non zero ep max packet size to 0xFFFF

usb device controller driver initializes all endpoint's max packet
size to 64 bytes. At the time of function driver bind gadget
framework chooses endpoint to use by comparing it with endpoint
descriptor of the function driver in ep_matches(). Driver bind
fails for the function driver having isochronous endpoints, as
ep max packet size is less than endpoint descriptor's max packet
size. Hence set ep max packet size to 0xFFFF for non-zero
endpoints in gadget driver registartion and endpoint disable.

Change-Id: I9fc0a19bd4502812b8659222d60274ad8b9fef34
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>