staging: pi433: Rename enum optionOnOff in rf69_enum.h

Renames the enum optionOnOff and its values optionOn, optionOff to enum
option_on_off and OPTION_ON, OPTION_OFF. Fixes checkpatch.pl warnings:
"Avoid CamelCase: <optionOnOff>, <optionOn>, <optionOff>".

Signed-off-by: Simon Sandström <simon@nikanor.nu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>