ALSA: oxfw: Change the way to make PCM rules/constraints

In previous commit, this driver can get to know stream formations at
each supported sampling rates. This commit uses it to make PCM
rules/constraints and obsoletes hard-coded rules/constraints.

For this purpose, this commit adds 'struct snd_oxfw_stream_formation' and
snd_oxfw_stream_parse_format() to parse data channel formation of data
block.

According to datasheet of OXFW970/971, they support 32.0kHz to 196.0kHz.

As long as developers investigate, some devices are confirmed to have
several formats for the same sampling rate.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Acked-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>