warp7: Allocate specific region of memory to OPTEE

warp7: Allocate specific region of memory to OPTEE

Subtracts CONFIG_OPTEE_TZDRAM_SIZE from the available DRAM size.

On WaRP7 we simply define the OPTEE region as from the maximum DRAM address
minus CONFIG_OPTEE_TZDRAM_SIZE bytes.

Note the OPTEE boot process will itself subtract the DRAM region it lives
in from the memory map passed to Linux.

Signed-off-by: Bryan O'Donoghue <[email protected]>
Tested-by: Breno Lima <[email protected]>
Reviewed-by: Fabio Estevam <[email protected]>