libusb: Add transfer type filter to get correct ep

The need for this due to AICE having 3 interfaces
(EP1 IN-Interrupt, EP2 OUT-Bulk, EP6 IN-Bulk).
Without it, the function will choose first two endpoint as
read_ep/write_ep. This filter will check transfer types
when get endpoint-id. Without this patch, AICE will not
get correct endpoint.

Change-Id: I4da93c7de41cd19e5095b4bfb42078b21f40b678
Signed-off-by: Hellosun Wu <wujiheng.tw@gmail.com>
Reviewed-on: http://openocd.zylin.com/3218


Tested-by: jenkins
Reviewed-by: Hsiangkai Wang <hsiangkai@gmail.com>
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>