Added --mass-erase option for Kinetis devices to pyocd-flashtool.
Added --mass-erase option for Kinetis devices to pyocd-flashtool.

mesheven/pyOCD,wjzhang/pyOCD,flit/pyOCD,pyocd/pyOCD,pyocd/pyOCD,wjzhang/pyOCD,matthewelse/pyOCD,mesheven/pyOCD,mbedmicro/pyOCD,matthewelse/pyOCD,mbedmicro/pyOCD,flit/pyOCD,mbedmicro/pyOCD,matthewelse/pyOCD,mesheven/pyOCD,wjzhang/pyOCD