media: i2c: max96717: Drop unused field assignment

The driver is not using gpio_chip::of_xlate() callback and hence
the of_gpio_n_cells assignment is unused. Drop it.

With that done, remove unneeded OF dependency and extend compile
test coverage.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Julien Massot <julien.massot@collabora.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>