3.12: build in configfs

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
3.12: enable HDMI on black

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
3.12: tweak beaglebone defconfig

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>