[ALSA] Add __devinit macro to at73c213 sound driver probe functions

This patch adds __devinit to the functions used when probing. Will also reduce
the memory footprint a bit if CONFIG_HOTPLUG is not enabled.

Signed-off-by: Hans-Christian Egtvedt <hcegtvedt@atmel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>