[media] atmel-isi: disable ISI even if it has codec request

In current code, stop_streaming() will just return if ISI is still
working in the codec. But this is incorrect, we need to disable ISI even
it is working on the codec, otherwise stop_streaming() will not work as
we expected.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>