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

src/compiler/mips/linkage-mips.cc

Index: src/compiler/mips/linkage-mips.cc
diff --git a/src/compiler/mips/linkage-mips.cc b/src/compiler/mips/linkage-mips.cc
index b3d3b91d8305e6457ac2406c31a278be9295fbc2..890ffb3a459c4f2f16460d4eb98c02653b06a9eb 100644
--- a/src/compiler/mips/linkage-mips.cc
+++ b/src/compiler/mips/linkage-mips.cc
@@ -21,20 +21,6 @@ struct MipsLinkageHelperTraits {
   static Register InterpreterDispatchTableReg() { return s1; }
   static Register RuntimeCallFunctionReg() { return a1; }
   static Register RuntimeCallArgCountReg() { return a0; }
-  static RegList CCalleeSaveRegisters() {
-    return s0.bit() | s1.bit() | s2.bit() | s3.bit() | s4.bit() | s5.bit() |
-           s6.bit() | s7.bit();
-  }
-  static RegList CCalleeSaveFPRegisters() {
-    return f20.bit() | f22.bit() | f24.bit() | f26.bit() | f28.bit() |
-           f30.bit();
-  }
-  static Register CRegisterParameter(int i) {
-    static Register register_parameters[] = {a0, a1, a2, a3};
-    return register_parameters[i];
-  }
-  static int CRegisterParametersLength() { return 4; }
-  static int CStackBackingStoreLength() { return 0; }
 };
 
 
@@ -65,12 +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);
 }