RISC-V: KVM: Exit run-loop immediately if xfer_to_guest fails

If xfer_to_guest_mode_handle_work() fails in the run-loop then exit
the run-loop immediately instead of doing it after some more work.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Anup Patel <anup@brainfault.org>