ALSA: ump: Don't open legacy substream for an inactive group

When a UMP Group is inactive, we shouldn't allow users to access it
via the legacy MIDI access.  Add the group active flag check and
return -ENODEV if it's inactive.

Link: https://patch.msgid.link/20241129094546.32119-2-tiwai@suse.de


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