staging: wilc1000: change handle_cfg_param's return type to void

When handle_cfg_param is called in hostIFthread that is a kernel thread,
it is not checked return type of this function. This patch changes
return type to void.

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