ALSA: fireworks: Add proc interface for debugging purpose

This commit adds proc interface to output infomation for debugging.
 - firmware information
 - sampling rate and clock source
 - physical metering (linear value)

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