PPC/s390: define VisitS128Select to fix compilation

R=joransiu@ca.ibm.com

Change-Id: Iabba5eb2cbd941ace02951995d727196763d1aca
Reviewed-on: https://chromium-review.googlesource.com/902363Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#51102}

src/compiler/ppc/instruction-selector-ppc.cc

@@ -2283,6 +2283,8 @@ void InstructionSelector::VisitF32x4Min(Node* node) { UNIMPLEMENTED(); }
 
 void InstructionSelector::VisitF32x4Max(Node* node) { UNIMPLEMENTED(); }
 
+void InstructionSelector::VisitS128Select(Node* node) { UNIMPLEMENTED(); }
+
 // static
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {

src/compiler/s390/instruction-selector-s390.cc

@@ -2602,6 +2602,8 @@ void InstructionSelector::VisitF32x4Min(Node* node) { UNIMPLEMENTED(); }
 
 void InstructionSelector::VisitF32x4Max(Node* node) { UNIMPLEMENTED(); }
 
+void InstructionSelector::VisitS128Select(Node* node) { UNIMPLEMENTED(); }
+
 // static
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {