[ALSA] dynamic minors (3/6): store device-specific object pointers dynamically

Instead of storing the pointers to the device-specific structures in an
array, put them into the struct snd_minor, and look them up dynamically.

This makes the device type modules independent of the minor number
encoding.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

sound/core/seq/seq_clientmgr.c

@@ -2531,7 +2531,7 @@ int __init snd_sequencer_device_init(void)
 		return -ERESTARTSYS;
 
 	if ((err = snd_register_device(SNDRV_DEVICE_TYPE_SEQUENCER, NULL, 0,
-				       &snd_seq_f_ops, "seq")) < 0) {
+				       &snd_seq_f_ops, NULL, "seq")) < 0) {
 		up(&register_mutex);
 		return err;
 	}