[media] e4000: implement controls via v4l2 control framework

Implement gain and bandwidth controls using v4l2 control framework.

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