These codes are written by me based on the privileged instruction set.
I tested it by qemu/riscv-probe.
Change-Id: I2e9e0c94e6518f63ade7680a3ce68bacfae219d4
Signed-off-by: Xiang Wang <wxjstz@126.com>
Reviewed-on: https://review.coreboot.org/28569
Reviewed-by: Philipp Hug <philipp@hug.cx>
Reviewed-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
