V4L/DVB: tvp514x: there is only one supported format, so simplify the code

Get rid of unnecessary code since this driver supports only one
pixel format. Removing this code will make the transition to the
mbus API easier as well.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Reviewed-by: Vaibhav Hiremath <hvaibhav@ti.com>
Tested-by: Vaibhav Hiremath <hvaibhav@ti.com>
Acked-by: Vaibhav Hiremath <hvaibhav@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>