Revert "intel: disable zero-copy TFP."

This reverts commit 94979950e8.

I've fixed it instead

src/mesa/drivers/dri/intel/intel_screen.c

@@ -391,12 +391,10 @@ intelHandleBufferAttach(__DRIdrawablePrivate *dPriv,
    intel_renderbuffer_set_region(rb, region);
 }
 
-#if 0
 static const __DRItexOffsetExtension intelTexOffsetExtension = {
    { __DRI_TEX_OFFSET },
    intelSetTexOffset,
 };
-#endif
 
 static const __DRItexBufferExtension intelTexBufferExtension = {
     { __DRI_TEX_BUFFER, __DRI_TEX_BUFFER_VERSION },
@@ -409,9 +407,7 @@ static const __DRIextension *intelScreenExtensions[] = {
     &driSwapControlExtension.base,
     &driFrameTrackingExtension.base,
     &driMediaStreamCounterExtension.base,
-#if 0
     &intelTexOffsetExtension.base,
-#endif
     &intelTexBufferExtension.base,
     NULL
 };