gpio: pxa: simplify BANK_OFF macro offset calculation

The macro BANK_OFF which calculates the base offset for each GPIO port.
The macro is needlessly complex and unreadable. Simplify the
calculation to a simple math operation.
Signed-off-by: Rob Herring <robh@kernel.org>
Cc: linux-gpio@vger.kernel.org
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-pxa.c

@@ -59,8 +59,7 @@
 #define GAFR_OFFSET	0x54
 #define ED_MASK_OFFSET	0x9C	/* GPIO edge detection for AP side */
 
-#define BANK_OFF(n)	(((n) < 3) ? (n) << 2 : ((n) > 5 ? 0x200 : 0x100)	\
-			+ (((n) % 3) << 2))
+#define BANK_OFF(n)	(((n) / 3) << 8) + (((n) % 3) << 2)
 
 int pxa_last_gpio;
 static int irq_base;