uwb: ensure that endpoint is interrupt

hwarc_neep_init() assumes that endpoint 0 is interrupt, but there's no
check for that, which results in a WARNING in USB core code, when a bad
USB descriptor is provided from a device:

usb 1-1: BOGUS urb xfer, pipe 1 != type 3
------------[ cut here ]------------
WARNING: CPU: 0 PID: 3 at drivers/usb/core/urb.c:449 usb_submit_urb+0xf8a/0x11d0
Modules linked in:
CPU: 0 PID: 3 Comm: kworker/0:0 Not tainted 4.13.0+ #111
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Workqueue: usb_hub_wq hub_event
task: ffff88006bdc1a00 task.stack: ffff88006bde8000
RIP: 0010:usb_submit_urb+0xf8a/0x11d0 drivers/usb/core/urb.c:448
RSP: 0018:ffff88006bdee3c0 EFLAGS: 00010282
RAX: 0000000000000029 RBX: ffff8800672a7200 RCX: 0000000000000000
RDX: 0000000000000029 RSI: ffff88006c815c78 RDI: ffffed000d7bdc6a
RBP: ffff88006bdee4c0 R08: fffffbfff0fe00ff R09: fffffbfff0fe00ff
R10: 0000000000000018 R11: fffffbfff0fe00fe R12: 1ffff1000d7bdc7f
R13: 0000000000000003 R14...