usb: raw-gadget: add copyright

Add copyright to drivers/usb/gadget/legacy/raw_gadget.c.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Link: https://lore.kernel.org/r/c8937266c4a5da073ac81cd471b18d869c984dfe.1611429174.git.andreyknvl@google.com


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