[media] vp702x: remove unused variable

struct vp702x_device_state.power_state is nowhere referenced.

Signed-off-by: Florian Mickler <florian@mickler.org>
Cc: Patrick Boettcher <pb@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>