gpio: grgpio: Do not use gc->pin2mask()

The pin2mask() accessor only shuffles BIT ORDER in big endian systems,
i.e. the bitstuffing is swizzled big endian so "bit 0" is bit 7 or
bit 15 or bit 31 or so.

The grgpio only uses big endian BYTE ORDER which will be taken car of
by the ->write_reg() callback.

Just use BIT(offset) to assign the bit.
Acked-by: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-grgpio.c

@@ -35,6 +35,7 @@
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/irqdomain.h>
+#include <linux/bitops.h>
 
 #define GRGPIO_MAX_NGPIO 32
 
@@ -96,12 +97,11 @@ static void grgpio_set_imask(struct grgpio_priv *priv, unsigned int offset,
 			     int val)
 {
 	struct gpio_chip *gc = &priv->gc;
-	unsigned long mask = gc->pin2mask(gc, offset);
 
 	if (val)
-		priv->imask |= mask;
+		priv->imask |= BIT(offset);
 	else
-		priv->imask &= ~mask;
+		priv->imask &= ~BIT(offset);
 	gc->write_reg(priv->regs + GRGPIO_IMASK, priv->imask);
 }