staging: wilc1000: handle_set_mac_address: rename result

This patch renames result to ret that is used to get return value from
wilc_send_config_pkt. It will be changed until all handle_*() function
has same variable name as ret.

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