ALSA: firewire-lib: include sound/asound.h to refer to snd_pcm_format_t

'snd_pcm_format_t' is used by amdtp_out_stream_set_pcm_format().

Currently, when just including amdtp.h, compiler cannot find this type because
this type is defined in uapi/sound/asound.h and this header is not included by
amdtp.h.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>