gadgetfs: ep_io - wait until IRQ finishes

after usb_ep_queue() if wait_for_completion_interruptible() is
interrupted we need to wait until IRQ gets finished.

Otherwise complete() from epio_complete() can corrupt stack.

Signed-off-by: Jozef Martiniak <jomajm@gmail.com>
Link: https://lore.kernel.org/r/20220708070645.6130-1-jomajm@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>