Revert: [APFloat] Fixed a bug in method 'fusedMultiplyAdd'.

This reverts revision 216913; the new test added at revision 216913
caused regression failures on a couple of buildbots.

llvm-svn: 216914
diff --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp
index ab641fd..7989e30 100644
--- a/llvm/lib/Support/APFloat.cpp
+++ b/llvm/lib/Support/APFloat.cpp
@@ -1801,7 +1801,7 @@
      extended-precision calculation.  */
   if (isFiniteNonZero() &&
       multiplicand.isFiniteNonZero() &&
-      addend.isFinite()) {
+      addend.isFiniteNonZero()) {
     lostFraction lost_fraction;
 
     lost_fraction = multiplySignificand(multiplicand, &addend);