Include device tree overlay for DVI-D with audio cape.

The DVI-D with audio cape is no longer supported in recent Debian images
but we can enable it by loading the device tree overlay manually.

Compile the .dts file using:
dtc -O dtb -o BB-BONE-DVID-02-00A0.dtbo -b 0 -@ BB-BONE-DVID-02-00A0.dts

Move the dtbo to /lib/firmware/ then enable the cape using:
echo BB-BONE-DVID-02 > /sys/devices/bone_capemgr*/slots