ALSA: mtpav: Allocate resources with device-managed APIs

This patch converts the resource management in mtpav driver with
devres as a clean up.  Each manual resource management is converted
with the corresponding devres helper now.

This should give no user-visible functional changes.

Link: https://lore.kernel.org/r/20210715075941.23332-75-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>