[PowerPC][NFC] Sorting out Pseudo related classes to avoid confusion

There are several Pseudo in PowerPC backend. 
eg:

* ISel Pseudo-instructions , which has let usesCustomInserter=1 in td 
ExpandISelPseudos -> EmitInstrWithCustomInserter will deal with them.
* Post-RA pseudo instruction, which has let isPseudo = 1 in td, or Standard pseudo (SUBREG_TO_REG,COPY etc.) 
ExpandPostRAPseudos -> expandPostRAPseudo will expand them
* Multi-instruction pseudo operations will expand them PPCAsmPrinter::EmitInstruction
* Pseudo instruction in CodeEmitter, which has encoding of 0.

Currently, in td files, especially PPCInstrVSX.td, 
we did not distinguish Post-RA pseudo instruction and Pseudo instruction in CodeEmitter very clearly.

This patch is to

* Rename Pseudo<> class to PPCEmitTimePseudo, which means encoding of 0 in CodeEmitter
* Introduce new class PPCPostRAExpPseudo <> for previous PostRA Pseudo
* Introduce new class PPCCustomInserterPseudo <> for previous Isel Pseudo

Differential Revision: https://reviews.llvm.org/D55143

llvm-svn: 349044
diff --git a/llvm/lib/Target/PowerPC/PPCInstrHTM.td b/llvm/lib/Target/PowerPC/PPCInstrHTM.td
index 6c4e212..0efe797 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrHTM.td
+++ b/llvm/lib/Target/PowerPC/PPCInstrHTM.td
@@ -20,8 +20,8 @@
   return getI32Imm (N->getZExtValue(), SDLoc(N));
 }]>;
 
-let hasSideEffects = 1, usesCustomInserter = 1  in {
-def TCHECK_RET : Pseudo<(outs crrc:$out), (ins), "#TCHECK_RET", []>;
+let hasSideEffects = 1 in {
+def TCHECK_RET : PPCCustomInserterPseudo<(outs crrc:$out), (ins), "#TCHECK_RET", []>;
 }