[media] media: platform: pxa_camera: make a standalone v4l2 device

This patch removes the soc_camera API dependency from pxa_camera.
In the current status :
 - all previously captures are working the same on pxa270
 - the s_crop() call was removed, judged not working
   (see what happens soc_camera_s_crop() when get_crop() == NULL)
 - if the pixel clock is provided by then sensor, ie. not MCLK, the dual
   stage change is not handled yet.
   => there is no in-tree user of this, so I'll let it that way

 - the MCLK is not yet finished, it's as in the legacy way,
   ie. activated at video device opening and closed at video device
   closing.
   In a subsequence patch pxa_camera_mclk_ops should be used, and
   platform data MCLK ignored. It will be the sensor's duty to request
   the clock and enable it, which will end in pxa_camera_mclk_ops.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>