riscv: hang on unhandled exceptions

Hang on unhandled exceptions to prevent execution in a faulty state.

Signed-off-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Rick Chen <rick@andestech.com>
1 file changed