MIPS32: Allow some patched instructions in delay slots

Test: test-art-host-gtest
Test: booted MIPS64 (with 2nd arch MIPS32R6) in QEMU
Test: test-art-target-gtest32
Test: testrunner.py --target --optimizing --32
Test: same tests as above on CI20
Test: booted MIPS32R2 in QEMU

Change-Id: I7e1ba59993008014d0115ae20c56e0a71fef0fb0
diff --git a/compiler/utils/label.h b/compiler/utils/label.h
index 85710d0..d835c63 100644
--- a/compiler/utils/label.h
+++ b/compiler/utils/label.h
@@ -31,9 +31,11 @@
 }  // namespace arm64
 namespace mips {
   class MipsAssembler;
+  class MipsLabel;
 }  // namespace mips
 namespace mips64 {
   class Mips64Assembler;
+  class Mips64Label;
 }  // namespace mips64
 namespace x86 {
   class X86Assembler;
@@ -114,7 +116,9 @@
 
   friend class arm64::Arm64Assembler;
   friend class mips::MipsAssembler;
+  friend class mips::MipsLabel;
   friend class mips64::Mips64Assembler;
+  friend class mips64::Mips64Label;
   friend class x86::X86Assembler;
   friend class x86::NearLabel;
   friend class x86_64::X86_64Assembler;