riscv: function to retrieve SBI implementation version

Provide function sbi_get_impl_version() to retrieve the SBI implementation
version.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
Reviewed-by: Rick Chen <rick@andestech.com>
2 files changed