drm/radeon/kms: add support for hw i2c on r1xx-r5xx

wire hw i2c support into radeon i2c algo.

fixes merged:
- handle bus probing correctly
- use meaningful error numbers
- abort if transaction fails
- The line mapping is different depending on the asic.
- protect hw i2c engine with a mutex
- rs300 doesn't have a pin select bit
- r200 has a different pin select setup

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
index f57480b..88113f7 100644
--- a/drivers/gpu/drm/radeon/radeon.h
+++ b/drivers/gpu/drm/radeon/radeon.h
@@ -829,6 +829,7 @@
 	struct r600_ih ih; /* r6/700 interrupt ring */
 	struct workqueue_struct *wq;
 	struct work_struct hotplug_work;
+	struct mutex dc_hw_i2c_mutex; /* display controller hw i2c mutex */
 
 	/* audio stuff */
 	struct timer_list	audio_timer;