arm64: defconfig: Enable ROCKCHIP_LVDS

Now, some of the rockchip hardware platforms do enable
lvds in mainline tree.

So, enable Rockchip LVDS driver via default defconfig.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Link: https://lore.kernel.org/r/20201109181017.206834-8-jagan@amarulasolutions.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>