staging: dwc2: validate urb->actual_length for OUT endpoints

In dwc2_assign_and_init_hc(), validate urb->actual_length for OUT
endpoints before using the value. This fix is from the Synopsys
vendor driver.

Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>