ALSA: maestro3: Allocate resources with device-managed APIs

This patch converts the resource management in PCI maestro3 driver
with devres as a clean up.  Each manual resource management is
converted with the corresponding devres helper, and the card object
release is managed now via card->private_free instead of a lowlevel
snd_device.  Superfluous ac97 private_free callbacks were dropped,
too.

This should give no user-visible functional changes.

Link: https://lore.kernel.org/r/20210715075941.23332-21-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>