Added missing lock on MEM_AP._read_memory().
Added missing lock on MEM_AP._read_memory().

mbedmicro/pyOCD,flit/pyOCD,mesheven/pyOCD,flit/pyOCD,mbedmicro/pyOCD,pyocd/pyOCD,mbedmicro/pyOCD,mesheven/pyOCD,mesheven/pyOCD,pyocd/pyOCD