Add override to overriden virtual methods, remove virtual keywords.

No functionality change. Changes made by clang-tidy + some manual cleanup.

llvm-svn: 217028
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp
index cff27ba..2d5857f 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp
@@ -80,7 +80,7 @@
 }
 
 /// Translates generic PPC fixup kind to Mach-O/PPC relocation type enum.
-/// Outline based on PPCELFObjectWriter::getRelocTypeInner().
+/// Outline based on PPCELFObjectWriter::GetRelocType().
 static unsigned getRelocType(const MCValue &Target,
                              const MCFixupKind FixupKind, // from
                                                           // Fixup.getKind()