[media] si2157: Si2148 support

Si2148-A20 silicon tuner support.

[Antti: Resolved conflict]

Signed-off-by: Evgeny Plehov <EvgenyPlehov@ukr.net>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>