drm/i915: Streamline gpio_mmio_base deduction

If we ignore the BXT situation, we can observe that the only variables
affecting gpio_mmio_base is IS_VALLEVIEW and HAS_GMCH_DISPLAY. The BXT
situation we can fit into the same pattern if we change gmbus_pins_bxt[]
to house the GMCH GPIO register offsets (like we do for all other
platfotms). So let's do that.

We could even simplify the VLV situation more by including the
display_mmio_offset in the GPIO register defines, but let's leave it be
for now.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1446672017-24497-13-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_i2c.c

@@ -63,9 +63,9 @@ static const struct gmbus_pin gmbus_pins_skl[] = {
 };
 
 static const struct gmbus_pin gmbus_pins_bxt[] = {
-	[GMBUS_PIN_1_BXT] = { "dpb", PCH_GPIOB },
-	[GMBUS_PIN_2_BXT] = { "dpc", PCH_GPIOC },
-	[GMBUS_PIN_3_BXT] = { "misc", PCH_GPIOD },
+	[GMBUS_PIN_1_BXT] = { "dpb", GPIOB },
+	[GMBUS_PIN_2_BXT] = { "dpc", GPIOC },
+	[GMBUS_PIN_3_BXT] = { "misc", GPIOD },
 };
 
 /* pin is expected to be valid */
@@ -628,12 +628,11 @@ int intel_setup_gmbus(struct drm_device *dev)
 
 	if (HAS_PCH_NOP(dev))
 		return 0;
-	else if (HAS_PCH_SPLIT(dev))
-		dev_priv->gpio_mmio_base = PCH_GPIOA - GPIOA;
-	else if (IS_VALLEYVIEW(dev))
+
+	if (IS_VALLEYVIEW(dev))
 		dev_priv->gpio_mmio_base = VLV_DISPLAY_BASE;
-	else
-		dev_priv->gpio_mmio_base = 0;
+	else if (!HAS_GMCH_DISPLAY(dev))
+		dev_priv->gpio_mmio_base = PCH_GPIOA - GPIOA;
 
 	mutex_init(&dev_priv->gmbus_mutex);
 	init_waitqueue_head(&dev_priv->gmbus_wait_queue);