parisc/power: Fix power soft-off when running on qemu

Firmware returns the physical address of the power switch,
so need to use gsc_writel() instead of direct memory access.

Fixes: d0c2194 ("parisc/power: Add power soft-off when running on qemu")
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org # v6.0+

drivers/parisc/power.c

@@ -176,7 +176,7 @@ static struct notifier_block parisc_panic_block = {
 static int qemu_power_off(struct sys_off_data *data)
 {
 	/* this turns the system off via SeaBIOS */
-	*(int *)data->cb_data = 0;
+	gsc_writel(0, (unsigned long) data->cb_data);
 	pdc_soft_power_button(1);
 	return NOTIFY_DONE;
 }