gpio: adp5588: get value from data out when dir is out

As discussed here: http://ez.analog.com/message/35852,
the 5587 revC and 5588 revB spec sheets contain a mistake
in the GPIO_DAT_STATx register description.

According to R.Shnell at ADI, as well as my own
observations, it should read:
"GPIO data status (shows GPIO state when read for inputs)".

This commit changes the get value function accordingly.

Signed-off-by: Jean-Francois Dagenais <[e-mail]>
Acked-by: Michael Hennerich <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

drivers/gpio/gpio-adp5588.c

···
 {
 	struct adp5588_gpio *dev =
 	    container_of(chip, struct adp5588_gpio, gpio_chip);
+	unsigned bank = ADP5588_BANK(off);
+	unsigned bit = ADP5588_BIT(off);
+	int val;
 
-	return !!(adp5588_gpio_read(dev->client,
-		  GPIO_DAT_STAT1 + ADP5588_BANK(off)) & ADP5588_BIT(off));
+	mutex_lock(&dev->lock);
+
+	if (dev->dir[bank] & bit)
+		val = dev->dat_out[bank];
+	else
+		val = adp5588_gpio_read(dev->client, GPIO_DAT_STAT1 + bank);
+
+	mutex_unlock(&dev->lock);
+
+	return !!(val & bit);
 }
 
 static void adp5588_gpio_set_value(struct gpio_chip *chip,