ALSA: opl3: Convert to snd_seq bus probe mechanism

ALSA: opl3: Convert to snd_seq bus probe mechanism

The snd_seq bus got a dedicated probe function. Make use of that. This
fixes a runtime warning about the driver needing to be converted to the
bus probe method.

Note that the remove callback returns void now. The actual return value
was ignored before (see device_remove() in drivers/base/dd.c), so there
is no problem introduced by converting `return -EINVAL` to `return`.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/fb5e44d995cf93b8feae22c4558598859712bc07.1765283601.git.u.kleine-koenig@baylibre.com