snd-firewire-lib: rename macro for AMDTP stream

AMDTP_STREAM_IN -> AMDTP_IN_STREAM
AMDTP_STREAM_OUT -> AMDTP_OUT_STREAM
snd-firewire-lib: modify comments
snd-firewire-lib: add amdtp_stream_set_params()

These functinos are obsoleted:
amdtp_stream_set_rate()
amdtp_stream_set_pcm()
amdtp_stream_set_midi()
snd-firewire-lib: modify some comments and MIDI related codes