gpio: grgpio: off by one in grgpio_to_irq()

"gc->ngpio" is a number between 1 and GRGPIO_MAX_NGPIO.  If "offset" is
GRGPIO_MAX_NGPIO then we're going one step beyond the end of the
priv->lirqs[] array.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-grgpio.c

@@ -121,7 +121,7 @@ static int grgpio_to_irq(struct gpio_chip *gc, unsigned offset)
 {
 	struct grgpio_priv *priv = grgpio_gc_to_priv(gc);
 
-	if (offset > gc->ngpio)
+	if (offset >= gc->ngpio)
 		return -ENXIO;
 
 	if (priv->lirqs[offset].index < 0)