hso: always read interface number from the current altsetting

Always read bInterfaceNumber from the current altsetting, not from the first one
available in the altsetting array. This is coming from code review, not related
to any specific bug.

Signed-off-by: Aleksander Morgado <aleksander@aleksander.es>
Signed-off-by: David S. Miller <davem@davemloft.net>