[media] radio: Add Sanyo LM7000 tuner driver

Add very simple driver for Sanyo LM7000 AM/FM tuner chip. Only FM is supported
as there is no known HW with AM implemented.

This will be used by radio-aimslab and radio-sf16fmi.

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>