Kick io-thread on qemu_chr_accept_input

Once a chr frontend is able to receive input again, we need to inform
the io-thread about this fact. Otherwise, main_loop_wait may continue to
select without the related backend file descriptor in its set. This can
cause high input latencies if only low-rate events arrive otherwise.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>

qemu-char.c

@@ -177,6 +177,7 @@ void qemu_chr_accept_input(CharDriverState *s)
 {
     if (s->chr_accept_input)
         s->chr_accept_input(s);
+    qemu_notify_event();
 }
 
 void qemu_chr_fe_printf(CharDriverState *s, const char *fmt, ...)