arm64: dts: ls1028a: Add properties for Mali DP500 node

The LS1028A has a LCD controller and Displayport interface that
connects to eDP and Displayport connectors on the LS1028A board.

This patch enables the LCD controller driver on the LS1028A.

Signed-off-by: Alison Wang <alison.wang@nxp.com>
Signed-off-by: Wen He <wen.he_1@nxp.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>