When the hardware can only deal with a monotonically increasing
appl_ptr, this flag can be set.

In case the application requests a rewind, be it with a
snd_pcm_rewind() or with a direct change of a mmap'ed pointer followed
by a SNDRV_PCM_IOCTL_SYNC_PTR, this patch checks if a rewind
occurred and returns an error.

Credits to Takashi Iwai for identifying the path with SYNC_PTR and
suggesting the pointer checks.
Suggested-by: NTakashi Iwai <tiwai@suse.de>
Reviewed-by: NTakashi Iwai <tiwai@suse.de>
Reviewed-by: NRanjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: NKai Vehmanen <kai.vehmanen@linux.intel.com>
Signed-off-by: NPierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20211119230852.206310-3-pierre-louis.bossart@linux.intel.comSigned-off-by: NMark Brown <broonie@kernel.org>