StgToCmm.cgTopBinding: no isNCG, use binBlobThresh
This is a one line change. It is a fixup from !7325 (closed), was pointed out in review of !7442 (merged), specifically: !7442 (merged) (comment 406581)
The change removes isNCG check from cgTopBinding and relies instead on checking that binBlobThresh is, or is not 0. This improves the cohesion of the module because more NCG related Backend stuff is moved into StgToCmm.Config. Note, that the meaning of a 0 in binBlobThresh is indicated in a comment next to its field in GHC.StgToCmm.Config