S390: Fix allocation-site-info.js failure

Mask used in MacroAssembler::TestJSArrayForAllocationMemento was not supposed
to shifted right by 16 bits before loaded in to register r0.

R=michael_dawson@ca.ibm.com,mbrandy@us.ibm.com,joransiu@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1852403002

Cr-Commit-Position: refs/heads/master@{#35247}

src/s390/macro-assembler-s390.cc

@@ -3558,27 +3558,25 @@ void MacroAssembler::TestJSArrayForAllocationMemento(Register receiver_reg,
       ExternalReference::new_space_allocation_top_address(isolate());
   const int kMementoMapOffset = JSArray::kSize - kHeapObjectTag;
   const int kMementoEndOffset = kMementoMapOffset + AllocationMemento::kSize;
-  Register mask = scratch2_reg;
 
-  DCHECK(!AreAliased(receiver_reg, scratch_reg, mask));
+  DCHECK(!AreAliased(receiver_reg, scratch_reg));
 
   // Bail out if the object is not in new space.
   JumpIfNotInNewSpace(receiver_reg, scratch_reg, no_memento_found);
 
   DCHECK((~Page::kPageAlignmentMask & 0xffff) == 0);
-  LoadImmP(mask, Operand((~Page::kPageAlignmentMask >> 16)));
   AddP(scratch_reg, receiver_reg, Operand(kMementoEndOffset));
 
   // If the object is in new space, we need to check whether it is on the same
   // page as the current top.
   XorP(r0, scratch_reg, Operand(new_space_allocation_top));
-  AndP(r0, r0, mask);
+  AndP(r0, r0, Operand(~Page::kPageAlignmentMask));
   beq(&top_check, Label::kNear);
   // The object is on a different page than allocation top. Bail out if the
   // object sits on the page boundary as no memento can follow and we cannot
   // touch the memory following it.
   XorP(r0, scratch_reg, receiver_reg);
-  AndP(r0, r0, mask);
+  AndP(r0, r0, Operand(~Page::kPageAlignmentMask));
   bne(no_memento_found);
   // Continue with the actual map check.
   b(&map_check, Label::kNear);