riscv: ae350: Enable CCTL_SUEN

CCTL operations are available to Supervisor/User-mode
software under the control of the mcache_ctl.CCTL_SUEN
control bit. Enable it to support Supervisor(and User)
CCTL operations.

Signed-off-by: Rick Chen <rick@andestech.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>