mac80211: extend/document powersave API

This modifies hardware flags for powersave to support three different
flags:
 * IEEE80211_HW_SUPPORTS_PS - indicates general PS support
 * IEEE80211_HW_PS_NULLFUNC_STACK - indicates nullfunc sending in software
 * IEEE80211_HW_SUPPORTS_DYNAMIC_PS - indicates dynamic PS on the device

It also adds documentation for all this which explains how to set the
various flags.

Additionally, it fixes a few things:
 * a spot where && was used to test flags
 * enable CONF_PS only when associated again

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/Documentation/DocBook/mac80211.tmpl b/Documentation/DocBook/mac80211.tmpl
index bdf908a..8af6d96 100644
--- a/Documentation/DocBook/mac80211.tmpl
+++ b/Documentation/DocBook/mac80211.tmpl
@@ -17,8 +17,7 @@
     </authorgroup>
 
     <copyright>
-      <year>2007</year>
-      <year>2008</year>
+      <year>2007-2009</year>
       <holder>Johannes Berg</holder>
     </copyright>
 
@@ -223,6 +222,11 @@
 !Finclude/net/mac80211.h ieee80211_key_flags
     </chapter>
 
+    <chapter id="powersave">
+      <title>Powersave support</title>
+!Pinclude/net/mac80211.h Powersave support
+    </chapter>
+
     <chapter id="qos">
       <title>Multiple queues and QoS support</title>
       <para>TBD</para>