arm64: dts: Add HDLCD support on Juno platforms

ARM's Juno platforms have two HDLCD controllers, each linked to an NXP
TDA19988 HDMI transmitter that provides output encoding. Add them
to the device tree.

Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>