[media] stb6100: get rid of tuner_state at struct stb6100_state

The stb6100 driver has a struct tuner_state on its state
struct, that it is used only to store the bandwidth. Even so,
this struct is not really used, as every time the bandwidth
is get or set, it goes through the hardware.

So, get rid of that.

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>