s390/3270: use diagnose 0x210 for device sensing under z/VM

There is a debugging leftover from git commit 4d334fd155b53adf
"s390/3270: asynchronous size sensing" in raw3270_reset_device_cb.
Under z/VM the diagnose 0x210 can be used to find the correct
size of the 3270 terminal.

Signed-off-by: Martin Schwidefsky <[e-mail]>

drivers/s390/char/raw3270.c

···
 	if (rq->rc) {
 		/* Reset command failed. */
 		rp->state = RAW3270_STATE_INIT;
-	} else if (0 && MACHINE_IS_VM) {
+	} else if (MACHINE_IS_VM) {
 		raw3270_size_device_vm(rp);
 		raw3270_size_device_done(rp);
 	} else