staging: wilc1000: rename pu8MacAddr in host_int_del_station

This patch changes pu8MacAddr to mac_addr that is second argument of
this function to avoid camelcase.

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