i965/nir: Enable NIR lowering of txf and rect offsets
This fixes the following piglit tests on gen6+:
tex-miplevel-selection textureProjGradOffset 2DRect
tex-miplevel-selection textureGradOffset 2DRect
tex-miplevel-selection textureGradOffset 2DRectShadow
tex-miplevel-selection textureProjGradOffset 2DRect_ProjVec4
tex-miplevel-selection textureProjGradOffset 2DRectShadow
Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Cc: "12.0" <mesa-dev@lists.freedesktop.org>