[arm64] Add operator== for CPURegister

The operator== in RegisterBase only compares the reg_code. On arm64 we have
another 'base', CPURegister. Before this change, registers from different
classes but with the same register number would compare as equal.
For example, x30 == d30 would be true, which is incorrect.

Change-Id: I8f19139df3f041b07bfa0883ec5ca768ef540802
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1745475Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Rodolph Perfetta <rodolph.perfetta@arm.com>
Cr-Commit-Position: refs/heads/master@{#63145}

src/codegen/arm64/register-arm64.h

@@ -151,13 +151,21 @@ class CPURegister : public RegisterBase<CPURegister, kRegAfterLast> {
   }
   bool IsValid() const { return reg_type_ != kNoRegister; }
   bool IsNone() const { return reg_type_ == kNoRegister; }
-  bool Is(const CPURegister& other) const {
+  constexpr bool Is(const CPURegister& other) const {
     return Aliases(other) && (reg_size_ == other.reg_size_);
   }
-  bool Aliases(const CPURegister& other) const {
+  constexpr bool Aliases(const CPURegister& other) const {
     return (reg_code_ == other.reg_code_) && (reg_type_ == other.reg_type_);
   }
 
+  constexpr bool operator==(const CPURegister& other) const {
+    return Is(other);
+  }
+
+  constexpr bool operator!=(const CPURegister& other) const {
+    return !(*this == other);
+  }
+
   bool IsZero() const;
   bool IsSP() const;