ALSA: firewire-lib: pool ideal sequence of syt offset and data block

In current implementation, sequence of syt offset and the number of data
blocks is generated when packets for outgoing stream are going to be
queued.

This commit generates and pools the sequence independently of the
processing of outgoing packets for future extension.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20200508043635.349339-10-o-takashi@sakamocchi.jp


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