usb: gadget: mass_storage: Remove repeated verbose license text

remove it because SPDX-License-Identifier is already used

Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Link: https://lore.kernel.org/r/20210822043005.192-1-caihuoqing@baidu.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>