Add Ssdbltrp trap handler support for S-mode double trap handling. If
the trap is received while in VS-mode, then the trap is redirected to
S-mode. If caught while in HS-mode, then an error is returned to the top
trap handler which will panic.
Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Samuel Holland <samuel.holland@sifive.com>