Mark the permanent map for radeon registers read-only. Failure to set this flag

allowed writing to the registers by any user that can open the DRI device, and
therefore ability to initiate DMA.  This came in with the merge from DRI CVS on
2005-04-15.

Approved by:	re (scottl)
Obtained from:	DRM CVS

sys/dev/drm/radeon_cp.c

@@ -2032,7 +2032,8 @@ int radeon_preinit(struct drm_device *dev, unsigned long flags)
 	}
 
 	ret = drm_initmap(dev, drm_get_resource_start(dev, 2),
-			  drm_get_resource_len(dev, 2), 2, _DRM_REGISTERS, 0);
+			  drm_get_resource_len(dev, 2), 2, _DRM_REGISTERS,
+			  _DRM_READ_ONLY);
 	if (ret != 0)
 		return ret;