ALSA: seq: Add port inactive flag

This extends the ALSA sequencer port capability bit to indicate the
"inactive" flag.  When this flag is set, the port is essentially
invisible, and doesn't appear in the port query ioctls, while the
direct access and the connection to this port are still allowed.  The
active/inactive state can be flipped dynamically, so that it can be
visible at any time later.

This feature is introduced basically for UMP; some UMP Groups in a UMP
Block may be unassigned, hence those are practically invisible.  On
ALSA sequencer, the corresponding sequencer ports will get this new
"inactive" flag to indicate the invisible state.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20230523075358.9672-27-tiwai@suse.de


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