ALSA: seq: ump: Notify port changes to system port

For allowing applications to track the FB active changes, this patch
adds the notification from the system port at each time a FB change is
handled and the active flag or re-grouping happens.

Link: https://lore.kernel.org/r/20230612081054.17200-8-tiwai@suse.de


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