aconnect: Show sequencer sound card numer/PID via aconnect

aconnect: Show sequencer sound card numer/PID via aconnect

rawmidi devices expose the card number via IOCTLs, which allows to
find the corresponding device in sysfs.

The sequencer provides no identifing data. Chromium works around this
issue by scanning rawmidi as well as sequencer devices and matching
them by using assumtions, how the kernel register sequencer devices.

This patch adds support for displaying the sound card number/PID to
aconnect.

Signed-off-by: Martin Koegler <martin.koegler@chello.at>
Signed-off-by: Takashi Iwai <tiwai@suse.de>