ALSA: azt3328: Put __maybe_unused for inline functions for gameport

Some inline functions are unused depending on kconfig, and the recent
change for clang builds made those handled as errors with W=1.
For avoiding pitfalls, mark those with __maybe_unused attributes.

Link: https://patch.msgid.link/20250813153628.12303-1-tiwai@suse.de


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