Canonicalize header guards into a common format.

Add header guards to files that were missing guards. Remove #endif comments
as they don't seem common in LLVM (we can easily add them back if we decide
they're useful)

Changes made by clang-tidy with minor tweaks.

llvm-svn: 215558
diff --git a/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoderCommon.h b/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoderCommon.h
index 3a6dbcd..bec4f0e 100644
--- a/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoderCommon.h
+++ b/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoderCommon.h
@@ -14,8 +14,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef X86DISASSEMBLERDECODERCOMMON_H
-#define X86DISASSEMBLERDECODERCOMMON_H
+#ifndef LLVM_LIB_TARGET_X86_DISASSEMBLER_X86DISASSEMBLERDECODERCOMMON_H
+#define LLVM_LIB_TARGET_X86_DISASSEMBLER_X86DISASSEMBLERDECODERCOMMON_H
 
 #include "llvm/Support/DataTypes.h"