drm/i915: Don't complain about stolen conflicts on gen3

Apparently stuff works that way on those machines.

I agree with Chris' concern that this is a bit risky but imo worth a
shot in -next just for fun. Afaics all these machines have the pci
resources allocated like that by the BIOS, so I suspect that it's all
ok.

This regression goes back to

commit eaba1b8f33
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Thu Jul 4 12:28:35 2013 +0100

    drm/i915: Verify that our stolen memory doesn't conflict

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76983
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=71031
Tested-by: lu hua <huax.lu@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: Paul Menzel <paulepanter@users.sourceforge.net>
Cc: stable@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/i915_gem_stolen.c

@@ -137,7 +137,11 @@ static unsigned long i915_stolen_to_physical(struct drm_device *dev)
 		r = devm_request_mem_region(dev->dev, base + 1,
 					    dev_priv->gtt.stolen_size - 1,
 					    "Graphics Stolen Memory");
-		if (r == NULL) {
+		/*
+		 * GEN3 firmware likes to smash pci bridges into the stolen
+		 * range. Apparently this works.
+		 */
+		if (r == NULL && !IS_GEN3(dev)) {
 			DRM_ERROR("conflict detected with stolen region: [0x%08x - 0x%08x]\n",
 				  base, base + (uint32_t)dev_priv->gtt.stolen_size);
 			base = 0;