drm/radeon/kms: get HPD info for connectors

This populates the connectors with HPD (Hot Plug Detect)
information.  This will be used in subsequent patches
for automatic digital monitor connect/disconnect handling.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/r500_reg.h b/drivers/gpu/drm/radeon/r500_reg.h
index 7baa739..74ad89b 100644
--- a/drivers/gpu/drm/radeon/r500_reg.h
+++ b/drivers/gpu/drm/radeon/r500_reg.h
@@ -716,6 +716,8 @@
 
 #define AVIVO_DVOA_BIT_DEPTH_CONTROL			0x7988
 
+#define AVIVO_DC_GPIO_HPD_A                 0x7e94
+
 #define AVIVO_GPIO_0                        0x7e30
 #define AVIVO_GPIO_1                        0x7e40
 #define AVIVO_GPIO_2                        0x7e50