[arm64] Fix some signed/unsigned type inconsistencies.

src/arm64/macro-assembler-arm64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_ARM64
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 191 matching lines @@
 
     // Mov instructions can't move immediate values into the stack pointer, so
     // set up a temporary register, if needed.
     UseScratchRegisterScope temps(this);
     Register temp = rd.IsSP() ? temps.AcquireSameSizeAs(rd) : rd;
 
     // Iterate through the halfwords. Use movn/movz for the first non-ignored
     // halfword, and movk for subsequent halfwords.
     DCHECK((reg_size % 16) == 0);
     bool first_mov_done = false;
-    for (unsigned i = 0; i < (rd.SizeInBits() / 16); i++) {
+    for (int i = 0; i < (rd.SizeInBits() / 16); i++) {
       uint64_t imm16 = (imm >> (16 * i)) & 0xffffL;
       if (imm16 != ignored_halfword) {
         if (!first_mov_done) {
           if (invert_move) {
             movn(temp, (~imm16) & 0xffffL, 16 * i);
           } else {
             movz(temp, imm16, 16 * i);
           }
           first_mov_done = true;
         } else {
@@ skipping 4841 matching lines @@
 }
 
 
 #undef __
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64