staging: wfx: remove unused do_probe

The identifier do_probe is unused since "staging: wfx: remove workaround
to send probe requests"

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200115135338.14374-61-Jerome.Pouiller@silabs.com


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