MipsAsmBackend.cpp, PPCAsmBackend.cpp: Fix -Asserts build to appease msvc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145894 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp b/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
index 12e0b3d..34a5774 100644
--- a/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
+++ b/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
@@ -100,6 +100,7 @@
                             const MCAsmLayout &Layout) const {
     // FIXME.
     assert(0 && "RelaxInstruction() unimplemented");
+    return false;
   }