Revert of [turbofan] Add alignment parameter to StackSlot operator

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

Index: src/compiler/mips/instruction-selector-mips.cc
diff --git a/src/compiler/mips/instruction-selector-mips.cc b/src/compiler/mips/instruction-selector-mips.cc
index 7ccc85520a8eef8a8f6fc1f2a2e695afb04d35b1..137ef0a704db0e1a762342fb889b9e5b8db83dbe 100644
--- a/src/compiler/mips/instruction-selector-mips.cc
+++ b/src/compiler/mips/instruction-selector-mips.cc
@@ -256,16 +256,6 @@
   VisitBinop(selector, node, opcode, false, kArchNop);
 }
 
-void InstructionSelector::VisitStackSlot(Node* node) {
-  StackSlotRepresentation rep = StackSlotRepresentationOf(node->op());
-  int alignment = rep.alignment();
-  int slot = frame_->AllocateSpillSlot(rep.size(), alignment);
-  OperandGenerator g(this);
-
-  Emit(kArchStackSlot, g.DefineAsRegister(node),
-       sequence()->AddImmediate(Constant(slot)),
-       sequence()->AddImmediate(Constant(alignment)), 0, nullptr);
-}
 
 void InstructionSelector::VisitLoad(Node* node) {
   LoadRepresentation load_rep = LoadRepresentationOf(node->op());