sunxi: change RMR64's RVBAR address for H6

Allwinner H6 has a different RVBAR address with A64/H5.

Add conditional RVBAR configuration into the code which does RMR switch.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com>