usb: gadget: mass_storage: use module_usb_composite_driver to simplify the code

module_usb_composite_driver() makes the code simpler by
eliminating boilerplate code.

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
1 file changed