[media] soc-camera: Continue the power off sequence if one of the steps fails

Powering off a device is a "best effort" task: failure to execute one of
the steps should not prevent the next steps to be executed. For
instance, an I2C communication error when putting the chip in stand-by
mode should not prevent the more agressive next step of turning the
chip's power supply off.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>