ads7846: make the suspend function sleep instead of busy poll

ads7846_suspend was busily polling for a couple of variables,
which never get a chance to change state unless kernel pre-emption
is enabled.  Use msleep instead.
Signed-off-by: Juha Yrjölä <juha.yrjola@nokia.com>

drivers/input/touchscreen/ads7846.c

@@ -443,7 +443,7 @@ ads7846_suspend(struct spi_device *spi, pm_message_t message)
 
 		while (ts->pendown || ts->pending) {
 			spin_unlock_irqrestore(&ts->lock, flags);
-			udelay(10);
+			msleep(1);
 			spin_lock_irqsave(&ts->lock, flags);
 		}
 	}