Input: atmel_mxt_ts - downgrade warning about empty interrupts

In the case where the CHG/interrupt line mode is not configured correctly,
this warning is output to dmesg output for each interrupt. Downgrade the
message to debug.
Signed-off-by: Nick Dyer <nick.dyer@itdev.co.uk>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/touchscreen/atmel_mxt_ts.c

@@ -837,7 +837,12 @@ static irqreturn_t mxt_process_messages_t44(struct mxt_data *data)
 	count = data->msg_buf[0];
 
 	if (count == 0) {
-		dev_warn(dev, "Interrupt triggered but zero messages\n");
+		/*
+		 * This condition is caused by the CHG line being configured
+		 * in Mode 0. It results in unnecessary I2C operations but it
+		 * is benign.
+		 */
+		dev_dbg(dev, "Interrupt triggered but zero messages\n");
 		return IRQ_NONE;
 	} else if (count > data->max_reportid) {
 		dev_err(dev, "T44 count %d exceeded max report id\n", count);