drm/radeon/kms: allow "invalid" DB formats as a means to disable DB

Signed-off-by: Marek Olšák <maraeo@gmail.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/evergreend.h b/drivers/gpu/drm/radeon/evergreend.h
index d3bd098..7934785 100644
--- a/drivers/gpu/drm/radeon/evergreend.h
+++ b/drivers/gpu/drm/radeon/evergreend.h
@@ -1277,6 +1277,8 @@
 #define   S_028044_FORMAT(x)                           (((x) & 0x1) << 0)
 #define   G_028044_FORMAT(x)                           (((x) >> 0) & 0x1)
 #define   C_028044_FORMAT                              0xFFFFFFFE
+#define	    V_028044_STENCIL_INVALID			0
+#define	    V_028044_STENCIL_8				1
 #define   G_028044_TILE_SPLIT(x)                       (((x) >> 8) & 0x7)
 #define DB_Z_READ_BASE					0x28048
 #define DB_STENCIL_READ_BASE				0x2804c