cactus: map memory regions, used as RX/TX buffers in SPM

To demonstrate implementation of memory-regions in SPM create RX/TX
buffers for each cactus VM. A VM will only map its allocated RX/TX
memory region.
The RX/TX regions start at 0x7200000 in Trusted DRAM. Each RX/TX buffer
pair in a VM will be of size 2 pages one for each of them.

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: I7d9dc5d82415d9543d4b9583ed6dca0d1f40b1cb
2 files changed