sunxi: switch PRCM to non-secure on H3/H5 SoCs

sunxi: switch PRCM to non-secure on H3/H5 SoCs

The PRCM of H3/H5 SoCs have a secure/non-secure switch, which controls
the access to some clock/power related registers in PRCM.

Current Linux kernel will access the CPUS (AR100) clock in the PRCM
block, so the PRCM should be switched to non-secure.

Add code to switch the PRCM to non-secure.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Tested-by: Chen-Yu Tsai <wens@csie.org>
Reviewed-by: Jagan Teki <jagan@openedev.com>