[media] siano: use USB endpoint descriptors for in/out endp

Instead of using hardcoded descriptors, detect them from the
USB descriptors.
This patch is rebased form Doron Cohen's patch:
	http://patchwork.linuxtv.org/patch/7883/



Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>