Input: ads7846 - allow specifying irq trigger type in platform data

On some platforms, for example with GPIO interrupts on mpc5121,
it is not possible to configure falling edge interrupts.

Specifying irq trigger type in platform data structure
allows using ads7846 driver on such platforms.

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index a9fdf55..69210cb5 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -1174,7 +1174,10 @@
 		goto err_put_regulator;
 	}
 
-	if (request_irq(spi->irq, ads7846_irq, IRQF_TRIGGER_FALLING,
+	if (!pdata->irq_flags)
+		pdata->irq_flags = IRQF_TRIGGER_FALLING;
+
+	if (request_irq(spi->irq, ads7846_irq, pdata->irq_flags,
 			spi->dev.driver->name, ts)) {
 		dev_info(&spi->dev,
 			"trying pin change workaround on irq %d\n", spi->irq);