drm: complete fix for drm_scatter.h

Another issue from the macro conversion.
Signed-off-by: Dave Airlie <airlied@linux.ie>

drivers/char/drm/drm_scatter.h

@@ -209,7 +209,7 @@ int DRM(sg_free)( struct inode *inode, struct file *filp,
 	drm_scatter_gather_t request;
 	drm_sg_mem_t *entry;
 
-	if (drm_core_check_feature(dev, DRIVER_SG))
+	if (!drm_core_check_feature(dev, DRIVER_SG))
 		return -EINVAL;
 
 	if ( copy_from_user( &request,