Vulkan: Remove CommandQueue::mQueueSerialMutex This mutex lock is no longer used and needed, thus removed in this CL. Also removed unused BufferAccess enum class. Bug: b/261737134 Change-Id: I7391e84c5b2abcd87de6ce9e66ba85f81ff7dce3 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4086934 Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Yuxin Hu <yuxinhu@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>