forked from Mirrors/opensbi

The latest RISC-V privileged specification introduces xenvcfg CSRs to enable/disable certain features/extensions for lower privilege modes. This patch adds defines for these new [m|h|s]envcfg CSRs. Signed-off-by: Anup Patel <apatel@ventanamicro.com> Reviewed-by: Atish Patra <atishp@rivosinc.com> Reviewed-by: Xiang W <wxjstz@126.com>