arm64: dts: allwinner: h6: Add RSB controller node

The H6 SoC contains an undocumented but fully functional RSB controller.
Add support for it. The MMIO register address matches other SoCs of the
same generation, and the IRQ matches a hole in the documented IRQ list.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
[wens@csie.org: Use raw numbers instead of macros for clock/reset index]
Signed-off-by: Chen-Yu Tsai <wens@csie.org>