Input: atmel_mxt_ts - use mxt_acquire_irq in mxt_soft_reset

If using IRQF_TRIGGER_FALLING, then there is a race here: if the reset
completes before we enable the IRQ, then CHG is already low and touch
will be broken.

This has been seen on Chromebook Pixel 2.

A workaround is to reconfig T18 COMMSCONFIG to enable the RETRIGEN bit
using mxt-app:
    mxt-app -W -T18 44
    mxt-app --backup
Tested-by: Tom Rini <trini@konsulko.com>
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

@@ -1093,6 +1093,19 @@ static int mxt_t6_command(struct mxt_data *data, u16 cmd_offset,
 	return 0;
 }
 
+static int mxt_acquire_irq(struct mxt_data *data)
+{
+	int error;
+
+	enable_irq(data->irq);
+
+	error = mxt_process_messages_until_invalid(data);
+	if (error)
+		return error;
+
+	return 0;
+}
+
 static int mxt_soft_reset(struct mxt_data *data)
 {
 	struct device *dev = &data->client->dev;
@@ -1111,7 +1124,7 @@ static int mxt_soft_reset(struct mxt_data *data)
 	/* Ignore CHG line for 100ms after reset */
 	msleep(100);
 
-	enable_irq(data->irq);
+	mxt_acquire_irq(data);
 
 	ret = mxt_wait_for_completion(data, &data->reset_completion,
 				      MXT_RESET_TIMEOUT);
@@ -1466,19 +1479,6 @@ static int mxt_update_cfg(struct mxt_data *data, const struct firmware *cfg)
 	return ret;
 }
 
-static int mxt_acquire_irq(struct mxt_data *data)
-{
-	int error;
-
-	enable_irq(data->irq);
-
-	error = mxt_process_messages_until_invalid(data);
-	if (error)
-		return error;
-
-	return 0;
-}
-
 static int mxt_get_info(struct mxt_data *data)
 {
 	struct i2c_client *client = data->client;