ALSA: emux: prune unused parameter from snd_soundfont_load_guspatch()

The `client` parameter was not used, so eliminate it from the call
chain.

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Message-ID: <20240406064830.1029573-3-oswald.buddenhagen@gmx.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>