[media] e4000: implement PLL lock v4l control

Implement PLL lock control to get PLL lock flag status from tuner
synthesizer.

Cc: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>