MIPS: Use weak cells in map checks in polymorphic ICs.

Port 45a36948

Fix typo in the mips ports.

BUG=

Review URL: https://codereview.chromium.org/767623003

Cr-Commit-Position: refs/heads/master@{#25590}

src/mips/macro-assembler-mips.cc

@@ -4033,7 +4033,7 @@ void MacroAssembler::LoadWeakValue(Register value, Handle<WeakCell> cell,
                                    Label* miss) {
   li(value, Operand(cell));
   lw(value, FieldMemOperand(value, WeakCell::kValueOffset));
-  JumpIfNotSmi(value, miss);
+  JumpIfSmi(value, miss);
 }
 
 

src/mips64/macro-assembler-mips64.cc

@@ -4000,7 +4000,7 @@ void MacroAssembler::LoadWeakValue(Register value, Handle<WeakCell> cell,
                                    Label* miss) {
   li(value, Operand(cell));
   ld(value, FieldMemOperand(value, WeakCell::kValueOffset));
-  JumpIfNotSmi(value, miss);
+  JumpIfSmi(value, miss);
 }