ALSA: compress: Add procfs info file for compressed nodes

This patch implements a procfs info file for compr nodes when
SND_VERBOSE_PROCFS is enabled. This is equivalent to what the PCM
core already does for pcm nodes.

Signed-off-by: Richard Fitzgerald <rf@opensource.wolfsonmicro.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>