media: pxa_camera: rename the soc_camera_ prefix to pxa_camera_

Rename soc_camera to pxa_camera as this has no longer anything to do with the old
soc_camera driver/framework. It's confusing when grepping on soc_camera.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>