apic: do not dereference pointer before it is checked for NULL

Right now you only get to apic_init_reset if you have an APIC
(do_cpu_init is reached only if CPU_INTERRUPT_INIT is set and
that only happens in hw/intc/apic.c).  However, this is wrong
because for example a port 92 or keyboard controller reset is
really an INIT, and that can happen also with no APIC.  So
keep the check and fix the error that Coverity reported.
Reported-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/intc/apic_common.c

@@ -177,13 +177,14 @@ bool apic_next_timer(APICCommonState *s, int64_t current_time)
 
 void apic_init_reset(DeviceState *dev)
 {
-    APICCommonState *s = APIC_COMMON(dev);
-    APICCommonClass *info = APIC_COMMON_GET_CLASS(s);
+    APICCommonState *s;
+    APICCommonClass *info;
     int i;
 
-    if (!s) {
+    if (!dev) {
         return;
     }
+    s = APIC_COMMON(dev);
     s->tpr = 0;
     s->spurious_vec = 0xff;
     s->log_dest = 0;
@@ -208,6 +209,7 @@ void apic_init_reset(DeviceState *dev)
     }
     s->timer_expiry = -1;
 
+    info = APIC_COMMON_GET_CLASS(s);
     if (info->reset) {
         info->reset(s);
     }