[InstSimplify] use any-zero matcher for fcmp folds

The m_APFloat matcher does not work with anything but strict
splat vector constants, so we could miss these folds and then
trigger an assertion in instcombine:
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=13201

The previous attempt at this in rL354406 had a logic bug that
actually triggered a regression test failure, but I failed to
notice it the first time.

llvm-svn: 354467