gallium/u_vbuf: add a faster path for uploading non-interleaved attribs
+1% higher FPS in torcs, though some testing showed even 1.9% higher FPS, so I guess it's the average is 1.4%.
+1% higher FPS in torcs, though some testing showed even 1.9% higher FPS, so I guess it's the average is 1.4%.