ALSA: core: Make snd_card_disconnect() return void

ALSA: core: Make snd_card_disconnect() return void

All callers from other files ignore the return value of this function.
And it can only ever return a non-zero value if the parameter card is NULL.

Move the check for card being NULL into snd_card_free_when_closed() to keep
the previous behaviour. Note this isn't necessary for
snd_card_disconnect_sync() because if card was NULL in there the dereference
of card for dev_err() would oops the kernel. Replace this by an oops
triggered by the dereference of card for spin_lock_irq().

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Acked-by: Geoff Levand <geoff@infradead.org>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20230207191907.467756-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>