Override the TLI callback enableAggressiveFMAFusion and return true. Indeed, fmul...

Override the TLI callback enableAggressiveFMAFusion and return true. Indeed, fmul, fmadd and fadd nodes cost the same number of cycles, so we can enable more combining heuristics to produce more fmadd nodes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225984 91177308-0d34-0410-b5e6-96231b3b80d8