media: i2c: Drop unused s5k6aa camera sensor driver

The s5k6aa camera sensor driver doesn't support DT and relies on
platform data. The last board files supplying platform data for that
device have been removed from the kernel in v3.11. The driver hasn't
been used since them. Drop it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>