drm: add framebuffer maps

The patch makes drmAddBufs/drmMapBufs can handle buffers in video memory

The attached patch adds a new buffer type DRM_FB_BUFFER. It works like
AGP memory but uses video memory.

From: Austin Yuan <austinyuan@viatech.com.cn>
Signed-off-by: Dave Airlie <airlied@linux.ie>
diff --git a/drivers/char/drm/drm.h b/drivers/char/drm/drm.h
index 50c4d98..3a4745f 100644
--- a/drivers/char/drm/drm.h
+++ b/drivers/char/drm/drm.h
@@ -369,7 +369,8 @@
 	enum {
 		_DRM_PAGE_ALIGN = 0x01, /**< Align on page boundaries for DMA */
 		_DRM_AGP_BUFFER = 0x02, /**< Buffer is in AGP space */
-		_DRM_SG_BUFFER  = 0x04  /**< Scatter/gather memory buffer */
+		_DRM_SG_BUFFER  = 0x04, /**< Scatter/gather memory buffer */
+		_DRM_FB_BUFFER  = 0x08  /**< Buffer is in frame buffer */
 	}	      flags;
 	unsigned long agp_start; /**< 
 				  * Start address of where the AGP buffers are