staging: r8188eu: res_to_status is unused

The function res_to_status is not used. Remove it.

Acked-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Acked-by: Michael Straube <straube.linux@gmail.com>
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20211016181343.3686-2-martin@kaiser.cx


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