Add missing include of <mutex>

This fixes build failure with clang-r522817

Bug: 322868540
Change-Id: Ie5db4a32bebd137d1ba11213e0d642d85f1f7d1d
Test: m out/soong/.intermediates/hardware/interfaces/automotive/can/1.0/default/tests/fuzzer/automotiveCanV1.0_fuzzer/android_vendor_arm64_armv8-2a_cortex-a55_fuzzer/e560d7b19ebf7276b3e850d3d346dec8/obj/hardware/interfaces/automotive/can/1.0/default/CanBus.o