RISC-V: KVM: selftests: Add ebreak test support

Initial support for RISC-V KVM ebreak test. Check the exit reason and
the PC when guest debug is enabled. Also to make sure the guest could
handle the ebreak exception without exiting to the VMM when guest debug
is not enabled.

Signed-off-by: Chao Du <duchao@eswincomputing.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20240402062628.5425-4-duchao@eswincomputing.com


Signed-off-by: Anup Patel <anup@brainfault.org>