ALSA: doc: Use DEFINE_SIMPLE_DEV_PM_OPS()

Use the new DEFINE_SIMPLE_DEV_PM_OPS() instead of SIMPLE_DEV_PM_OPS()
for the example code.  This allows us to drop CONFIG_PM_SLEEP ifdefs.

While we're at it, expand the driver definition instead of passing
directly via .driver.pm field.  This seems to be a more common
pattern.

Signed-off-by: Takashi Iwai <tiwai@suse.de>