V4L/DVB (6333): cx88: Change void* card_priv to struct vp3054_i2c_state

card_priv was only used to store a pointer to the vp3054 state struct.
There's no need to use a void * since it doesn't have multiple types.

Make the field conditional on VP3045 support.  It was already conditional on
DVB support, but it's only used if VP3045 support is on, so that makes for a
better option to check.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Reviewed-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>