arm: mvebu: AC5: Use finer grained memory map

The ATF implementation for AC5/AC5X ends up with bl31 living in some
internal SRAM. This is in the middle of the large MMIO region that we
were using. Adjust this to be finer grained blocks based on the address
map from the AC5X Family Control and Management Subsystem Functional
Datasheet.

Signed-off-by: Chris Packham <judge.packham@gmail.com>