ALSA: oxygen: Convert to EXPORT_SIMPLE_DEV_PM_OPS()

Use the newer EXPORT_SIMPLE_DEV_PM_OPS() macro instead of
SIPLE_DEV_PM_OPS() and manual export, together with pm_ptr() macro,
which makes CONFIG_PM_SLEEP ifdefs superfluous.

Merely a cleanup, there should be no actual code change.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20250313170731.26943-8-tiwai@suse.de