rockchip: add common aarch32 support

rockchip: add common aarch32 support

There are a number or ARMv7 Rockchip SoCs that are very similar in their
bringup routines to the existing arm64 SoCs, so there is quite a high
commonality possible here.

Things like virtualization also need psci and hyp-mode and instead of
trying to cram this into bootloaders like u-boot, barebox or coreboot
(all used in the field), re-use the existing infrastructure in TF-A
for this (both Rockchip plat support and armv7 support in general).

So add core support for aarch32 Rockchip SoCs, with actual soc support
following in a separate patch.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Change-Id: I298453985b5d8434934fc0c742fda719e994ba0b