[PowerPC] Support @tls in the asm parser

This adds support for the last missing construct to parse TLS-related
assembler code:
   add 3, 4, symbol@tls

The ADD8TLS currently hard-codes the @tls into the assembler string.
This cannot be handled by the asm parser, since @tls is parsed as
a symbol variant.  This patch changes ADD8TLS to have the @tls suffix
printed as symbol variant on output too, which allows us to remove
the isCodeGenOnly marker from ADD8TLS.  This in turn means that we
can add a AsmOperand to accept @tls marked symbols on input.

As a side effect, this means that the fixup_ppc_tlsreg fixup type
is no longer necessary and can be merged into fixup_ppc_nofixup.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185692 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/PowerPC/MCTargetDesc/PPCMCCodeEmitter.cpp

@@ -209,7 +209,7 @@ unsigned PPCMCCodeEmitter::getTLSRegEncoding(const MCInst &MI, unsigned OpNo,
   // hint to the linker that this statement is part of a relocation sequence.
   // Return the thread-pointer register's encoding.
   Fixups.push_back(MCFixup::Create(0, MO.getExpr(),
-                                   (MCFixupKind)PPC::fixup_ppc_tlsreg));
+                                   (MCFixupKind)PPC::fixup_ppc_nofixup));
   return CTX.getRegisterInfo()->getEncodingValue(PPC::X13);
 }