ALSA: oxfw: use managed-resource to maintain model-specific data

ALSA oxfw driver allocates memory objects for data specific to some
models. These objects are used to maintain functionalities specific
to the models for ALSA rawMIDI/control interfaces. They can be
released as managed-resource of 'struct snd_card.card_dev'.

This commit uses managed-resource of the sound card device for this
purpose.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>