arm64: dts: rockchip: set display regulators to always-on on BPI-R2-Pro

The gpu power supply needs to stay always on until the issues with power-
domains not being regulator aware is resolved. Otherwise we run into
issues where the gpu-regulator gets shut down and we start getting mmu
faults.

Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Link: https://lore.kernel.org/r/20220606170803.478082-2-linux@fw-web.de
Signed-off-by: Heiko Stuebner <heiko@sntech.de>