touchscreen: Fix sign bug

platform_get_irq_byname() can return negative results, it is not seen to
unsigned ts_irq. Make it signed.
Signed-off-by: Kulikov Vasiliy <segooon@gmail.com>
Acked-By: Luotao Fu <l.fu@pengutronix.de>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/input/touchscreen/stmpe-ts.c

@@ -269,7 +269,7 @@ static int __devinit stmpe_input_probe(struct platform_device *pdev)
 	struct input_dev *idev;
 	struct stmpe_ts_platform_data *ts_pdata = NULL;
 	int ret = 0;
-	unsigned int ts_irq;
+	int ts_irq;
 
 	ts_irq = platform_get_irq_byname(pdev, "FIFO_TH");
 	if (ts_irq < 0)