ALSA: seq: Register kernel port with full information

ALSA: seq: Register kernel port with full information

The current ALSA sequencer core tries to register the new kernel
sequencer port on the list at first, then fill up the port
information.  This means that user-space may sneak the wrong
information before the actual data is filled, which isn't ideal.
Although the user-space should try to query the port info after the
port registration notification is sent out, it'd be still better to
have a port available with the full info from the beginning.

This patch changes the sequencer port creation and registration
procedure; now split to two steps, for creation and insertion, and the
port is registered after the information is filled.

Link: https://sashiko.dev/#/patchset/20260518194023.1667857-1-maoyixie.tju%40gmail.com
Link: https://patch.msgid.link/20260519094254.465041-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>