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

Add conditional RVBAR configuration into the code which does RMR switch.
Signed-off-by: NIcenowy Zheng <icenowy@aosc.io>
Reviewed-by: NAndre Przywara <andre.przywara@arm.com>
Acked-by: NMaxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: NJagan Teki <jagan@openedev.com>
Tested-by: NJagan Teki <jagan@amarulasolutions.com>