soc: sunxi: Move power-domain driver to the genpd dir

To simplify with maintenance let's move the sunxi power-domain driver to
the new genpd directory. Going forward, patches are intended to be managed
through a separate git tree, according to MAINTAINERS.

Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Jernej Skrabec <jernej.skrabec@gmail.com>
Cc: Samuel Holland <samuel@sholland.org>
Cc: <linux-sunxi@lists.linux.dev>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/genpd/Makefile

@@ -9,3 +9,4 @@ obj-y					+= renesas/
 obj-y					+= rockchip/
 obj-y					+= samsung/
 obj-y					+= starfive/
+obj-y					+= sunxi/

drivers/genpd/sunxi/Makefile

+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_SUN20I_PPU)		+= sun20i-ppu.o

drivers/soc/sunxi/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
 obj-$(CONFIG_SUNXI_MBUS) +=	sunxi_mbus.o
 obj-$(CONFIG_SUNXI_SRAM) +=	sunxi_sram.o
-obj-$(CONFIG_SUN20I_PPU) +=	sun20i-ppu.o