staging: wilc1000: remove wilc_set_start_scan_req declaration

This patch deletes wilc_set_start_scan_req declaration. It is not find
wilc_set_start_scan_req definition in this driver.

Signed-off-by: Chaehyun Lim <chaehyun.lim@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>