gallivm: fix bogus aos path detection

gallivm: fix bogus aos path detection

Need to check the wrap mode of the actually used coords not a fixed 2.
While checking more than necessary would only potentially disable aos and
not cause any harm I'm pretty sure for 3d textures it could have caused
assertion failures (if s,t coords have simple filter and r not).

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>