forked from Mirrors/opensbi

If a standard event was not found in the list of events that are handled by harts but belongs to the standard event list defined by the specification, return SBI_ENOTSUPP. Without that, we can not distinguish a non implemented standard event from a non valid one. Signed-off-by: Clément Léger <cleger@rivosinc.com> Reviewed-by: Samuel Holland <samuel.holland@sifive.com> Reviewed-by: Atish Patra <atishp@rivosinc.com>