soc: rockchip: Fix compile-testing SoC drivers

Similar to commit 7f94b69e ("ARM: ixp4xx: fix compile-testing soc
drivers").

drivers/soc/rockchip/Kconfig makes plenty of provision for configuring
drivers either for ARCH_ROCKCHIP or for COMPILE_TEST. But
drivers/soc/Makefile pulls the rug out from under us, by refusing to
build anything if we specified COMPILE_TEST but not ARCH_ROCKCHIP.

Currently, I'm not aware of anything that breaks without this patch, but
it certainly makes for confusing builds (CONFIG_ROCKCHIP_PM_DOMAINS=y,
but we didn't actually compile the driver?) and leaves room for future
error (I have pending patches that break confusingly with COMPILE_TEST=y
even though their Kconfig dependencies seem correct [1]).

Defer to drivers/soc/rockchip/{Makefile,Kconfig} to do the right thing.

[1] e.g.,
https://lore.kernel.org/linux-rockchip/20220405184816.RFC.2.I2d73b403944f0b8b5871a77585b73f31ccc62999@changeid/
[RFC PATCH 2/2] PM / devfreq: rk3399_dmc: Block PMU during transitions
Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220425184503.v3.3.Id5f16dec920f620120c0a143a97a12e16d401760@changeidSigned-off-by: Heiko Stuebner <heiko@sntech.de>

drivers/soc/Makefile

@@ -22,7 +22,7 @@ obj-y				+= microchip/
 obj-y				+= amlogic/
 obj-y				+= qcom/
 obj-y				+= renesas/
-obj-$(CONFIG_ARCH_ROCKCHIP)	+= rockchip/
+obj-y				+= rockchip/
 obj-$(CONFIG_SOC_SAMSUNG)	+= samsung/
 obj-$(CONFIG_SOC_SIFIVE)	+= sifive/
 obj-y				+= sunxi/