ALSA: firewire-lib: schedule hardware IRQ according to the size of PCM period

ALSA: firewire-lib: schedule hardware IRQ according to the size of PCM period

ALSA IEC 61883-1/6 packet streaming engine controls 1394 OHCI controller
to generate hardware IRQ for fixed number of isochronous packets (=16)
since its first commit.

This commit allow the engine to generate it for variable period according
to the number of event to handle. For outgoing stream, internal
calculator is used to check the accumulated events. For incoming stream,
the number of data block in the packet of stream is used to check the
accumulated events. When it's unavailable, fixed number of packet
roughly calculated in advance is used instead of event counting.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20191017155424.885-11-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>