Update AArch32 VIXL intrinsics w.r.t. the new art::ReadBarrier API.

Update with respect to changes introduced by commit
12b58b23de974232e991c650405f929f8b0dcc9f.

Test: ART_USE_READ_BARRIER=true make
Change-Id: Iaefd664172ff19cce17cf4d3b2064dba86170c22
diff --git a/compiler/optimizing/intrinsics_arm_vixl.cc b/compiler/optimizing/intrinsics_arm_vixl.cc
index 2e37a00..6ff0ca4 100644
--- a/compiler/optimizing/intrinsics_arm_vixl.cc
+++ b/compiler/optimizing/intrinsics_arm_vixl.cc
@@ -2024,7 +2024,7 @@
     //   if (src_ptr != end_ptr) {
     //     uint32_t rb_state = Lockword(src->monitor_).ReadBarrierState();
     //     lfence;  // Load fence or artificial data dependency to prevent load-load reordering
-    //     bool is_gray = (rb_state == ReadBarrier::gray_ptr_);
+    //     bool is_gray = (rb_state == ReadBarrier::GrayState());
     //     if (is_gray) {
     //       // Slow-path copy.
     //       do {
@@ -2065,9 +2065,8 @@
     // Given the numeric representation, it's enough to check the low bit of the
     // rb_state. We do that by shifting the bit out of the lock word with LSRS
     // which can be a 16-bit instruction unlike the TST immediate.
-    static_assert(ReadBarrier::white_ptr_ == 0, "Expecting white to have value 0");
-    static_assert(ReadBarrier::gray_ptr_ == 1, "Expecting gray to have value 1");
-    static_assert(ReadBarrier::black_ptr_ == 2, "Expecting black to have value 2");
+    static_assert(ReadBarrier::WhiteState() == 0, "Expecting white to have value 0");
+    static_assert(ReadBarrier::GrayState() == 1, "Expecting gray to have value 1");
     __ Lsrs(temp2, temp2, LockWord::kReadBarrierStateShift + 1);
     // Carry flag is the last bit shifted out by LSRS.
     __ B(cs, read_barrier_slow_path->GetEntryLabel());