Fix subframe assembly
Backport of Rudi's work
https://github.com/warped-rudi/linux-linaro-stable-mx6/commit/48b9658c2204c835dd5459bb58e684d2063b24f6
Set validity bit in HDMI and SPDIF according to channel status
From Rudi (Openbrick) :
https://github.com/OpenBricks/openbricks/blob/master/config/platforms/arm/imx6/machines/utilite/packages/linux/patches/11-Set-validity-bit-in-HDMI-and-SPDIF-according-to-chan.patch