V4L/DVB (7927): ivtv: simplify gpio initialization for XCeive tuners.

Separate gpio_init field and xceive_pin and combine the two when
the gpio is initialized. So there is no longer any need to set the
xceive pin in the gpio_init values, simplifying the creation of a
new card definition.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>