[media] cxusb: Add read_mac_address for TT CT2-4400 and CT2-4650

Read MAC address from the EEPROM.

This version two corrects a flaw in the result code returning that
did exist in the first version.

Signed-off-by: Olli Salonen <olli.salonen@iki.fi>
Reviewed-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>