s390x/sclpconsole-lm: Fix hanging SCLP line mode console

Trigger recalculating sets of file descriptors for the main loop's poll()
in order to make sure a possibly removed FD 0 from the poll() file
descriptor array is re-added. FD 0 is removed from the decriptor array
when the console's can_read() callback returns 0.
Signed-off-by: NHeinz Graalfs <graalfs@linux.vnet.ibm.com>
Reviewed-by: NDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: NCornelia Huck <cornelia.huck@de.ibm.com>

hw/char/sclpconsole-lm.c

@@ -128,6 +128,7 @@ static int get_console_data(SCLPEvent *event, uint8_t *buf, size_t *size,
     cons->length = 0;
     /* data provided and no more data pending */
     event->event_pending = false;
+    qemu_notify_event();
     return 0;
 }