[media] tw686x: Support VIDIOC_{S,G}_PARM ioctls

Now that the frame rate can be properly set, this commit adds support
for S_PARM and G_PARM.

Signed-off-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>