BUG: only override vector size for avx code
BUG: only override vector size for avx code

only a fraction of code has avx variants so the size must not be
overriden globally.
Closes gh-12507

ahaldane/numpy,rgommers/numpy,rgommers/numpy,pizzathief/numpy,pbrod/numpy,endolith/numpy,charris/numpy,pbrod/numpy,simongibbons/numpy,jakirkham/numpy,WarrenWeckesser/numpy,jakirkham/numpy,ahaldane/numpy,numpy/numpy,mattip/numpy,mattip/numpy,jorisvandenbossche/numpy,mhvk/numpy,mhvk/numpy,mhvk/numpy,numpy/numpy,jorisvandenbossche/numpy,WarrenWeckesser/numpy,seberg/numpy,pdebuyl/numpy,seberg/numpy,numpy/numpy,mattip/numpy,MSeifert04/numpy,mhvk/numpy,grlee77/numpy,shoyer/numpy,charris/numpy,jorisvandenbossche/numpy,jorisvandenbossche/numpy,abalkin/numpy,MSeifert04/numpy,pizzathief/numpy,simongibbons/numpy,pizzathief/numpy,grlee77/numpy,endolith/numpy,charris/numpy,madphysicist/numpy,pbrod/numpy,WarrenWeckesser/numpy,WarrenWeckesser/numpy,anntzer/numpy,jakirkham/numpy,MSeifert04/numpy,madphysicist/numpy,shoyer/numpy,mhvk/numpy,madphysicist/numpy,pdebuyl/numpy,pizzathief/numpy,abalkin/numpy,charris/numpy,jakirkham/numpy,jorisvandenbossche/numpy,grlee77/numpy,abalkin/numpy,simongibbons/numpy,pdebuyl/numpy,seberg/numpy,endolith/numpy,jakirkham/numpy,pbrod/numpy,shoyer/numpy,pdebuyl/numpy,numpy/numpy,MSeifert04/numpy,grlee77/numpy,WarrenWeckesser/numpy,simongibbons/numpy,pbrod/numpy,seberg/numpy,ahaldane/numpy,MSeifert04/numpy,rgommers/numpy,madphysicist/numpy,ahaldane/numpy,shoyer/numpy,anntzer/numpy,rgommers/numpy,mattip/numpy,anntzer/numpy,madphysicist/numpy,simongibbons/numpy,ahaldane/numpy,endolith/numpy,pizzathief/numpy,grlee77/numpy,anntzer/numpy,shoyer/numpy