staging: r8188eu: remove header usb_vendor_req.h

Nothing from the header usb_vendor_req.h is used in the driver code.
Remove the header.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20220407192819.10661-8-straube.linux@gmail.com


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