ALSA: seq: ump: Fix seq port updates per FB info notify

ALSA: seq: ump: Fix seq port updates per FB info notify

update_port_infos() is called when a UMP FB Info update notification
is received, and this function is supposed to update the attributes of
the corresponding sequencer port.  However, the function had a few
issues and it brought to the incorrect states.  Namely:

- It tried to get a wrong sequencer info for the update without
  correcting the port number with the group-offset 1
- The loop exited immediately when a sequencer port isn't present;
  this ended up with the truncation if a sequencer port in the middle
  goes away

This patch addresses those bugs.

Fixes: 4a16a3af0571 ("ALSA: seq: ump: Handle FB info update")
Link: https://patch.msgid.link/20241128170423.23351-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>