pcm: rate: fix last_commit_ptr boundary wrapping

pcm: rate: fix last_commit_ptr boundary wrapping

Wrap last_commit_ptr using boundary. Was just wrapped to 0, which is
correct only if the buffer size, and hence the boundary, is an integer
multiple of the period size.

Fixes: 467d69c5bc1 ("Fix CPU hog with combination of rate plugin")
Fixes: 29041c52207 ("fix infinite draining of the rate plugin in SND_PCM_NONBLOCK mode")
Link: https://lore.kernel.org/alsa-devel/20221230164814.901457-1-consult.awy@gmail.com/
Signed-off-by: Alan Young <consult.awy@gmail.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>