Fix issue with "Logitech Webcam C525":

Set a valid alternate interface setting
when enumerating USB audio devices else
the device mentioned will not work like
expected.

PR:		usb/178722
MFC after:	1 week
Fix rte leak introduced in r248070.

MFC after:	2 weeks
Don't clear stall at first time use of USB MIDI endpoints.
Most likely some non-USB compliant devices will choke on it
sooner or later. Clear stall is strictly speaking not needed.
If the first MIDI command sent or transmitted is lost, this
is not a big problem for us.

MFC after:	1 week