Not all tvp5150 variants support the same, for example some have an
internal signal generator that can output a black screen.

So the device id and rom version have to be stored in the driver's
state to know what variant is a given device.

While being there, remove some redundant comments about the device
version since there is already calls to v4l2_info() with that info.
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>