rockchip: video: rk_edp: add more rk3288 edp node options

The rk3288 DT synced from Linux contains some different
properties in the edp node then origanal used in U-boot.
Allow both options to be backwards compatible and to be able
to handle recent rk3288.dtsi files.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>