[ALSA] soc - neo1973_wm8753.c add suspend and shutdown hooks for lm4857 chip

Patch taken from the openmoko bugtracker
http://bugzilla.openmoko.org/cgi-bin/bugzilla/show_bug.cgi?id=781

This patch adds Suspend/Resume and Shutdown support for the lm4857 to
the driver.

Signed-off-by: Graeme Gregory <graeme@openmoko.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>