ALSA: ppc: fix unused function local variable

ALSA: ppc: fix unused function local variable

The function local variable is not used anymore, while it is left.

This commit deletes it.

Fixes: 25a5a77ae0bc ("ALSA: core: Make snd_card_free() return void")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Link: https://lore.kernel.org/r/20230209104823.45899e76@canb.auug.org.au/
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20230209002548.94496-1-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>