drm/i915: disable gmbus on i830

The hw just returns garbage.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=49838
Reported-and-tested-by: Vladyslav <DFEW.Entwickler@googlemail.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_i2c.c

@@ -490,6 +490,10 @@ int intel_setup_gmbus(struct drm_device *dev)
 		/* By default use a conservative clock rate */
 		bus->reg0 = port | GMBUS_RATE_100KHZ;
 
+		/* gmbus seems to be broken on i830 */
+		if (IS_I830(dev))
+			bus->force_bit = true;
+
 		intel_gpio_setup(bus, port);
 	}