usb: gadget: Add support for MBIM OS descriptor handling

In order to support MBIM in a multi-config usb composition
make use of composite gadget driver support for OS descriptor.
This allows Host to identify preferred configuration to choose.
Pass signature field, vendor code, compatibleID and
subCompatibleID from user space. Also remove redundant MBIM OS
descriptor related data structure definition in the driver.

Change-Id: I6fd8b950d53ef700be2d435e5973dd2c74525cd8
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
Signed-off-by: Chandana Kishori Chiluveru <cchiluve@codeaurora.org>