[turbofan] Factor C call descriptor building into compiler/c-linkage.cc.

src/compiler/ppc/linkage-ppc.cc

Index: src/compiler/ppc/linkage-ppc.cc
diff --git a/src/compiler/ppc/linkage-ppc.cc b/src/compiler/ppc/linkage-ppc.cc
index d9404bf89eae79ca3fc1d683d8cd51988ec52a6d..cfec9af941e7cdf8decb85b096e5f69d2e1e0992 100644
--- a/src/compiler/ppc/linkage-ppc.cc
+++ b/src/compiler/ppc/linkage-ppc.cc
@@ -21,19 +21,6 @@ struct PPCLinkageHelperTraits {
   static Register InterpreterDispatchTableReg() { return r15; }
   static Register RuntimeCallFunctionReg() { return r4; }
   static Register RuntimeCallArgCountReg() { return r3; }
-  static RegList CCalleeSaveRegisters() {
-    return r14.bit() | r15.bit() | r16.bit() | r17.bit() | r18.bit() |
-           r19.bit() | r20.bit() | r21.bit() | r22.bit() | r23.bit() |
-           r24.bit() | r25.bit() | r26.bit() | r27.bit() | r28.bit() |
-           r29.bit() | r30.bit() | fp.bit();
-  }
-  static RegList CCalleeSaveFPRegisters() { return 0; }
-  static Register CRegisterParameter(int i) {
-    static Register register_parameters[] = {r3, r4, r5, r6, r7, r8, r9, r10};
-    return register_parameters[i];
-  }
-  static int CRegisterParametersLength() { return 8; }
-  static int CStackBackingStoreLength() { return 0; }
 };
 
 
@@ -64,12 +51,6 @@ CallDescriptor* Linkage::GetStubCallDescriptor(
 }
 
 
-CallDescriptor* Linkage::GetSimplifiedCDescriptor(Zone* zone,
-                                                  const MachineSignature* sig) {
-  return LH::GetSimplifiedCDescriptor(zone, sig);
-}
-
-
 CallDescriptor* Linkage::GetInterpreterDispatchDescriptor(Zone* zone) {
   return LH::GetInterpreterDispatchDescriptor(zone);
 }