lib: utils/sys: Add CLINT memregion in the root domain

The CLINT memory should not be accessed by the supervisor-mode
software so let's protect it by adding CLINT memregion to the
root domain.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Xiang W <wxjstz@126.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>