media: pxa_camera: disable and unprepare the clock source on error

pxa_camera_probe() was not calling pxa_camera_deactivate(),
responsible to call clk_disable_unprepare(), on the failure path. This
was leading to unbalancing source clock.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>