arecordmidi2: Add passive mode and interactive mode

arecordmidi2: Add passive mode and interactive mode

Allow arecordmidi2 running without specifying the source ports via -p
option.  This will create a UMP Endpoint with the full 16 FBs, and
simply reads from the input ports via subscribers.  User needs to
connect to the ports manually, though.

Also, add -r option to run in the interactive mode.  In the
interactive mode, arecordmidi2 waits for the RETURN key entered from
the terminal to start the recording, and the recording ends after
another RETURN key.

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