ALSA: sh: Fix up namespace collision in sh_dac_audio.

The module_platform_driver() conversion ended up tripping over the driver
name, leading to confusion in the macro with regards to 'driver' being
redefined. rename it to something slightly more suitable to avoid
namespace collisions.

sound/sh/sh_dac_audio.c:444:122: error: conflicting types for 'driver_init'
include/linux/device.h:773:6: note: previous declaration of 'driver_init' was here
make[3]: *** [sound/sh/sh_dac_audio.o] Error 1

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>