ALSA: oxfw: use managed-resource to maintain cache of stream formats

ALSA oxfw driver allocates memory objects for cache of stream formats.
The objects are used to maintain packet streaming by components for
ALSA rawMIDI/PCM interface. 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>