media: soc_camera_platform: remove obsolete soc_camera test driver

This is a test stub driver for soc_camera. Since soc_camera is
being deprecated (and in fact, nobody is using it anymore)
there's no sense in keeping this test driver.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>