[ARM] Kirkwood: t5325: add audio support

This patch declares the i2c audio codec and initialise audio.
It's adding the alc5621 codec in the i2c board info and is calling
kirkwood_audio_init() to initialize kirkwood audio.

Signed-off-by: Arnaud Patard <arnaud.patard@rtp-net.org>
Signed-off-by: Nicolas Pitre <nico@fluxnic.net>