ALSA: firewire-lib: change waking up timing to process packets

When starting AMDTP domain, tasks in process context yields running CPU
till all of isochronous context get callback, with an assumption that
it's OK to process content of packet.

However several isochronous cycles are skipped to transfer rx packets, or
the content of rx packets are dropped, to manage the timing to start
processing the packets.

This commit changes the timing for tasks in process context to wake up
when processing content of packet is actually ready.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20210520040154.80450-9-o-takashi@sakamocchi.jp


Signed-off-by: Takashi Iwai <tiwai@suse.de>