ALSA: ppc: fix error return code in snd_pmac_probe()

If snd_pmac_tumbler_init() or snd_pmac_tumbler_post_init() fails,
snd_pmac_probe() need return error code.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20210616021121.1991502-1-yangyingliang@huawei.com


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