hw/xen_evtchn: Initialize flush_kvm_routes

In xen_evtchn_soft_reset() variable flush_kvm_routes can
be used before being initialized.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Oleg Sviridov <oleg.sviridov@red-soft.ru>
Signed-off-by: Artem Chernyshev <artem.chernyshev@red-soft.ru>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240329113939.257033-1-artem.chernyshev@red-soft.ru>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

hw/i386/kvm/xen_evtchn.c

@@ -1097,7 +1097,7 @@ static int close_port(XenEvtchnState *s, evtchn_port_t port,
 int xen_evtchn_soft_reset(void)
 {
     XenEvtchnState *s = xen_evtchn_singleton;
-    bool flush_kvm_routes;
+    bool flush_kvm_routes = false;
     int i;
 
     if (!s) {