fbdev/media: Use GPIO descriptors for VIA GPIO

The VIA fbdev exposes a custom GPIO chip for its GPIOs, these
are in turn looked up the camera driver using a custom API.

Drop the custom API, provide a look-up table and convert to
GPIO descriptors. Note proper polarity on the RESET line.

Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Helge Deller <deller@gmx.de>