V4L/DVB (9665): af9015: Add support for the Digittrade DVB-T USB Stick remote

Adds support for the Digittrade DVB-T USB Stick remote.
As the Digittrade USB stick identifies itself as a generic Afatech AF9015
device, the remote cannot be autodetected. To enable it, add the following
to /etc/modprobe.d/dvb-usb-af9015 or /etc/modprobe.conf:

options dvb-usb-af9015 remote=4

Signed-off-by: Alain Kalker <miki@dds.nl>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>