[PATCH] ipw2200: ipw_wx_set_essid fix

This patch cleanups the ipw_wx_set_essid code and forces a reassociation
when setting the essid to "any". I have tested this patch with iwconfig. It
makes ipw2200 compliant with all the cases mentioned in the iwconfig man
page. The commands

iwconfig iface essid any
iwconfig iface essid -- any
iwconfig iface essid off
iwconfig iface essid on

all seemed to work correctly. None of this worked before the patch.

Note, this patch treats

iwconfig iface essid
iwconfig iface essid ""

The same. It produces an error message: essid: Unknown host.
Since an essid of "" is not mentioned in the iwconfig man page.

Signed-off-by: Bill Moss <bmoss@clemson.edu>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>