Clean up the drivers with the new managed buffer allocation API.
The superfluous snd_pcm_lib_malloc_pages() and
snd_pcm_lib_free_pages() calls are dropped, as well as the superfluous
snd_pcm_lib_preallocate_free_for_all() call.  As of the result,
hw_free and pcm_destruct ops became empty and got removed.

Cc: Olivier Moysan <olivier.moysan@st.com>
Cc: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20191210142614.19405-13-tiwai@suse.deSigned-off-by: Mark Brown <broonie@kernel.org>