bebob: fix failure of mapping AMDTP channels

The direction for command is opposite.
fireworks/bebob: confirm to break/connection when stopping streams

In previous implementation, when no PCM streams exists, connection is not going
to be broken. But for prudence, connection is confirm to be broken in this case.
bebob: fix null pointer dereference of Yamaha mixer

The number of entries in clock_source array was much longer than actual count
because of using sizeof instad of ARRAY_SIZE().
bebob: move AV/C ccm commands

MAudio devices use 'Connection and Compatibility Management 1.0' to change its
clock source. This specification is defined by 1394TA. So moving these codes to
bebob_command.c.