ALSA: ac97_codec: merge WM9703 and WM9705 ops

The WM9705 and WM9703 ops are the same actually so use
the same code for both.

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>