arm: stm32mp: Implement support for TZC 400 controller

The purpose of this change is to allow configuring TrustZone (TZC)
memory permissions. For example, OP-TEE expects TZC regions to be
configured in a very particular way. The API presented here is
intended to allow exactly that.

UCLASS support is not implemented, because it would not be too useful.
Changing TZC permissions needs to be done with care, so as not to cut
off access to memory we are currently using. One place where we can
use this is at the end of SPL, right before jumping to OP-TEE.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>