Add atmel usba udc driver support, porting from Linux kernel

The original code in Linux Kernel information is as following

commit e01ee9f509a927158f670408b41127d4166db1c7
Author: Jingoo Han <jg1.han@samsung.com>
Date:   Tue Jul 30 17:00:51 2013 +0900

    usb: gadget: use dev_get_platdata()

    Use the wrapper function for retrieving the platform data instead of
    accessing dev->platform_data directly.

Signed-off-by: Bo Shen <voice.shen@atmel.com>