i965: Don't rebase the index buffer to min 0 if any arrays are in VBOs.

i965: Don't rebase the index buffer to min 0 if any arrays are in VBOs.

There was a check to only do the rebase if we didn't have everything
in VBOs, but nexuiz apparently hands us a mix of VBOs and arrays,
resulting in blocking on the GPU to do a rebase.

Improves nexuiz 800x600, high-settings performance on my Ironlake 41%
(+/- 1.3%), from 14.0fps to 19.7fps.