[wined3d] Remove arb_tex_npot for NV FX series in fixup_extensions

[Stefan Dösinger]

> this patch fixes performance regressions in Max Payne 2, Morrowind and
> HL2 on nVidia GeforceFx based hardware.
> It has been approved by Stefan Dösinger and verified by test
> application (see source).
Just to add this here as well, I think this patch is fine. I could not find
any way to use the NP2 emulation for conditional NP2 textures like on ATI
cards