s390/qdio: don't touch the dsci in tiqdio_add_input_queues()

BugLink: https://bugs.launchpad.net/bugs/1838467

commit ac6639cd upstream.

Current code sets the dsci to 0x00000080. Which doesn't make any sense,
as the indicator area is located in the _left-most_ byte.

Worse: if the dsci is the _shared_ indicator, this potentially clears
the indication of activity for a _different_ device.
tiqdio_thinint_handler() will then have no reason to call that device's
IRQ handler, and the device ends up stalling.

Fixes: d0c9d4a8 ("[S390] qdio: set correct bit in dsci")
Cc: <stable@vger.kernel.org>
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/s390/cio/qdio_thinint.c

@@ -80,7 +80,6 @@ void tiqdio_add_input_queues(struct qdio_irq *irq_ptr)
 	mutex_lock(&tiq_list_lock);
 	list_add_rcu(&irq_ptr->input_qs[0]->entry, &tiq_list);
 	mutex_unlock(&tiq_list_lock);
-	xchg(irq_ptr->dsci, 1 << 7);
 }
 
 void tiqdio_remove_input_queues(struct qdio_irq *irq_ptr)