Compute shaders don't have access to the framebuffer, so there's no
point in worrying whether a texture is bound as a render target.
This saves a bunch of resolves in GFXBench4 Manhattan 3.1, but doesn't
seem to impact performance at all, at least on Apollolake.
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
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