Drivers of ALSA firewire stack can process packets for IT/IR context in
process context when the process operates ALSA PCM character device by
calling ioctl(2) with some requests. The ioctl requests are:

 * SNDRV_PCM_IOCTL_HWSYNC
 * SNDRV_PCM_IOCTL_SYNC_PTR
 * SNDRV_PCM_IOCTL_REWIND
 * SNDRV_PCM_IOCTL_FORWARD
 * SNDRV_PCM_IOCTL_WRITEI_FRAMES
 * SNDRV_PCM_IOCTL_READI_FRAMES
 * SNDRV_PCM_IOCTL_WRITEN_FRAMES
 * SNDRV_PCM_IOCTL_READN_FRAMES

This means that general application can process PCM frames apart from
hardware IRQ invocation, even if they are programmed by either IRQ-based
scheduling model or Timer-based scheduling model.

This commit add support for Timer-based scheduling model by allowing
PCM runtime to suppress both process wakeup per period and scheduling
hardware IRQ.

SNDRV_PCM_INFO_BATCH is obsoleted since ALSA IEC 61883-1/6 packet streaming
engine can report the number of transferred PCM frames within PCM period
boundary. The granularity equals to SYT_INTERVAL in blocking transmission.
In non-blocking transmission, it doesn't equal to SYT_INTERVAL but doesn't
exceed.

This patch is tested with PulseAudio, and --sched-model option of axfer
with fix against the issue reported at:

 * https://lore.kernel.org/alsa-devel/687f9871-7484-1370-04d1-9c968e86f72b@linux.intel.com/#rSigned-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20210527123253.174315-1-o-takashi@sakamocchi.jpSigned-off-by: Takashi Iwai <tiwai@suse.de>