mfd: stmpe: Support gpio over irq under device tree

The stmpe_platform_data has a irq_over_gpio field, which allows the
system to read STMPE events whenever an IRQ occurs on a GPIO pin.
This patch adds the ability to configure this field and to use a GPIO
as an IRQ source for boards configuring the STMPE in device tree.
Signed-off-by: NSean Cross <xobs@kosagi.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

drivers/mfd/stmpe.c

@@ -1122,7 +1122,12 @@ static void stmpe_of_probe(struct stmpe_platform_data *pdata,
 	if (pdata->id < 0)
 		pdata->id = -1;
 
-	pdata->irq_trigger = IRQF_TRIGGER_NONE;
+	pdata->irq_gpio = of_get_named_gpio_flags(np, "irq-gpio", 0,
+				&pdata->irq_trigger);
+	if (gpio_is_valid(pdata->irq_gpio))
+		pdata->irq_over_gpio = 1;
+	else
+		pdata->irq_trigger = IRQF_TRIGGER_NONE;
 
 	of_property_read_u32(np, "st,autosleep-timeout",
 			&pdata->autosleep_timeout);