staging: wilc1000: wilc_msgqueue: use standard struct list_head

This patch uses standard struct list_head in struct message and
message_queue instead of custom linked list.

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