dvb-usb-dibusb-mc-common: Add MODULE_LICENSE

dvb-usb-dibusb-mc-common: Add MODULE_LICENSE

dvb-usb-dibusb-mc-common is licensed under GPLv2, and if we don't say
so then it won't even load since it needs a GPL-only symbol.

Reported-by: Dominique Dumont <dod@debian.org>
References: https://bugs.debian.org/853110
Cc: stable@vger.kernel.org # 4.9+
Fixes: e91455a1495a ("[media] dvb-usb: split out common parts of dibusb")
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Gbp-Pq: Topic bugfix/all
Gbp-Pq: Name media-dvb-usb-dibusb-mc-common-add-module_license.patch