[media] em28xx: support for 1b80:e425 MaxMedia UB425-TC

Hardware is based of:
Empia EM2874B
Micronas DRX 3913KA2
NXP TDA18271HDC2

Only DVB-C supported currently since missing firmware.
According to my tests, DRX 3913KA2 demodulator requires firmware
in order to support DVB-T mode.

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