drm/radeon/kms: fix r6xx+ scanout on BE systems

R6xx+ have per-block swappers.  BE content in the
framebuffer will now be swapped properly during scanout.
Untested, however, the same code is reported working in
the UMS ddx.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@gmail.com>
diff --git a/drivers/gpu/drm/radeon/r600_reg.h b/drivers/gpu/drm/radeon/r600_reg.h
index 33cda01..f869897 100644
--- a/drivers/gpu/drm/radeon/r600_reg.h
+++ b/drivers/gpu/drm/radeon/r600_reg.h
@@ -81,7 +81,11 @@
 #define R600_MEDIUM_VID_LOWER_GPIO_CNTL                            0x720
 #define R600_LOW_VID_LOWER_GPIO_CNTL                               0x724
 
-
+#define R600_D1GRPH_SWAP_CONTROL                               0x610C
+#       define R600_D1GRPH_SWAP_ENDIAN_NONE                    (0 << 0)
+#       define R600_D1GRPH_SWAP_ENDIAN_16BIT                   (1 << 0)
+#       define R600_D1GRPH_SWAP_ENDIAN_32BIT                   (2 << 0)
+#       define R600_D1GRPH_SWAP_ENDIAN_64BIT                   (3 << 0)
 
 #define R600_HDP_NONSURFACE_BASE                                0x2c04