allwinner: Add security setup

Some peripherals are TrustZone aware, so they need to be configured to
be accessible from non-secure world, as we don't need any of them being
exclusive to the secure world.
This affects some clocks, DMA channels and the Secure Peripheral
Controller (SPC). The latter controls access to most devices, but is not
active unless booting with the secure boot fuse burnt.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>