Use mutator lock for deoptimized_methods_

deoptimized_methods_ is always read when we hold shared mutator lock and
updated after suspending all threads when mutator lock is held
exclusively. So we can just use mutator lock instead of another special
lock.

Bug: 206029744
Test: art/test.py
Change-Id: I6596281abb8d723af80335a79a95c641b884fba6
2 files changed