amidi: Fix device list

amidi: Fix device list

From: Matthias Koenig <mk@phasorlab.de>

amidi does not show all devices with the --list-devices option.
It assumes that all output ports equals input ports and does not
show an input only port.
This patch extends the output of amidi -l by one column which shows
the input/output direction of each port.
E.g.

zebra:amidi # ./amidi -l
Dir Device    Name
IO  hw:1,0    MPU-401 MIDI 1-0
IO  hw:2,0,0  Keystation MIDI 1
IO  hw:3,0,0  Miditerminal 1
IO  hw:3,0,1  Miditerminal 2
IO  hw:3,0,2  Miditerminal 3
IO  hw:3,0,3  Miditerminal 4
I   hw:3,0,4  Miditerminal SMPTE