include: sbi: Use lower bits for domain memory region permissions

We should use lower bits for domain memory region access permissions
and higher bits for other domain memory region attributes. This helps
us use same bit assignment for parsing domain memory region access
permissions from device tree.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>