XHCI: trying to submit a transfer to a non-existent endpoint!

[waddlesplash]

This is the underlying cause of the (now-fixed) KDL in #12929.

Easily reproducible by plugging in an Android phone, setting it to USB MIDI mode, and then running find /dev:

KERN: usb hub 2: KERN: port 0: new device connected
KERN: usb xhci 0: cancel queued transfers for pipe 0xffffffff820d0e40 (0)
KERN: usb hub 2: KERN: port 0: new device connected
KERN: usb error hub 2: new device on a port that is already in use
KERN: usb xhci 0: cancel queued transfers for pipe 0xffffffff820d0e40 (0)
KERN: usb xhci 0: cancel queued transfers for pipe 0xffffffff96dbfa00 (0)
KERN: usb xhci 0: KERN: cancel queued transfers for pipe 0xffffffff96d9f750 (1)
KERN: usb xhci 0: KERN: cancel queued transfers for pipe 0xffffffff96d9f480 (1)
KERN: usb xhci 0: KERN: cancel queued transfers for pipe 0xffffffff96d9f430 (2)
KERN: check_sense: encountered DEFERRED ERROR - bye, bye
KERN: bt: bluetooth_std_ops: Connection Thread error
KERN: usb xhci 0: cancel queued transfers for pipe 0xffffffff82ce98e8 (1)
KERN: usb xhci 0: KERN: cancel queued transfers for pipe 0xffffffff81a9bc30 (2)
KERN: usb xhci 0: cancel queued transfers for pipe 0xffffffff818164d8 (2)
KERN: musb_midi: init_driver() version:Feb 23 2019 12:01:32
KERN: usb_midi: ...
...
KERN: usb error xhci 0: trying to submit a transfer to a non-existent endpoint!