chardev: fix parallel device can't be reconnect

Parallel device don't register be->chr_can_read function, but remote
disconnect event is handled in chr_read.So connected parallel device
can not detect remote disconnect event. The chardevs with chr_can_read=NULL
has the same problem.
Signed-off-by: NPeng Hao <peng.hao2@zte.com.cn>
Reviewed-by: NWang Yechao <wang.yechao255@zte.com.cn>
Reviewed-by: NJiang Biao <jiang.biao2@zte.com.cn>
Message-Id: <1499874119-67558-1-git-send-email-peng.hao2@zte.com.cn>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/char/parallel.c

@@ -503,6 +503,10 @@ static const VMStateDescription vmstate_parallel_isa = {
     }
 };
 
+static int parallel_can_receive(void *opaque)
+{
+     return 1;
+}
 
 static void parallel_isa_realizefn(DeviceState *dev, Error **errp)
 {
@@ -535,6 +539,8 @@ static void parallel_isa_realizefn(DeviceState *dev, Error **errp)
     isa_init_irq(isadev, &s->irq, isa->isairq);
     qemu_register_reset(parallel_reset, s);
 
+    qemu_chr_fe_set_handlers(&s->chr, parallel_can_receive, NULL,
+                             NULL, NULL, s, NULL, true);
     if (qemu_chr_fe_ioctl(&s->chr, CHR_IOCTL_PP_READ_STATUS, &dummy) == 0) {
         s->hw_driver = 1;
         s->status = dummy;