ALSA: AC97: Print AC97 flags in proc file to make debug it easier

While debugging some code paths in AC97 codec patches and its suspend
and resume functions, getting to know the flags has proved useful to
follow those code paths.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>