Sonypi: use synchronize_irq instead of sycnronize_sched

We know exactly what IRQ we are using, so synchronize_irq()
suits much better. Plus synchronize_sched() will not work
for us in -rt kernels.
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Acked-by: Mattia Dongili <malattia@linux.it>

drivers/char/sonypi.c

@@ -1434,7 +1434,7 @@ static int __devexit sonypi_remove(struct platform_device *dev)
 {
 	sonypi_disable();
 
-	synchronize_sched();  /* Allow sonypi interrupt to complete. */
+	synchronize_irq(sonypi_device.irq);
 	flush_scheduled_work();
 
 	if (useinput) {