sunxi: Select SUN8I_RSB more carefully

sunxi: Select SUN8I_RSB more carefully

SUN8I_RSB should not be selected by MACH_SUN8I, because the hardware
is not present in half of those SoCs (H3/H5, R40, and V3s). Move the
selection to the SoCs where the hardware actually exists.
As it currently stands, selecting that option also requires using it in
some way, which is not the case for one A80 board. Since we have only
three A80 boards in total, we select it their via their defconfigs.

Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Samuel Holland <samuel@sholland.org>
[Andre: fixing up Sunchip_CX-A99 build]
Signed-off-by: Andre Przywara <andre.przywara@arm.com>