allwinner: Add R_PRCM security setup for H6

allwinner: Add R_PRCM security setup for H6

H6 has a reorganized R_PRCM compared to A64/H5, with the security switch
at a different offset. Until now, we did not notice, because the switch
has no effect unless the secure mode e-fuse is blown.

Since we are adding more platform-specific CCU registers, move them to
their own header, and out of the memory map (where they do not belong).

Signed-off-by: Samuel Holland <samuel@sholland.org>
Change-Id: Ie77476db0515080954eaa2e32bf6c3de657cda86