staging: r8188eu: remove unused module parameter rtw_chip_version

staging: r8188eu: remove unused module parameter rtw_chip_version

The module parameter rtw_chip_version sets the chip_version field of
struct registry_priv but that field is never used in the driver code.
Remove the unused module parameter.

Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20220821123138.8070-1-straube.linux@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>