ALSA: sound/atmel/ac97c.c: Add device tree support

This adds device tree support for the AC97 controller. It uses the
soc-ac97link bindings, but actually only ac97-reset is used.

Signed-off-by: Alexander Stein <alexanders83@web.de>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>