staging: r8188eu: reg_rfoff is never set

The field reg_rfoff in struct pwrctrl_priv is never set. It stays at
its default value 0. Remove it and remove related dead code.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20220404082142.4639-3-straube.linux@gmail.com


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