Add documentation for passphrase option.

The wifi-iface actually supports an undocumented option to choose
whether to treat a passphrase as a text passphrase or an encoded
passphrase (like encoded by the wpa_passphrase utility). This patch
documents that functionality.

Signed-off-by: Warren Turkal <wt@penguintechs.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@17712 3c298f89-4303-0410-b956-a3cf2f4a3e73

docs/wireless.tex

@@ -117,6 +117,7 @@ config wifi-iface
     option key2     key 2
     option key3     key 3
     option key4     key 4
+    option passphrase 0,1
     option server   ip address
     option port     port
     option hidden   0,1
@@ -219,6 +220,13 @@ config wifi-iface
     \item \texttt{key, key1, key2, key3, key4} (wep, wpa and psk) \\
         WEP key, WPA key (PSK mode) or the RADIUS shared secret (WPA RADIUS mode)
 
+    \item \texttt{passphrase} (wpa) \\
+        0 treats the wpa psk as a text passphrase; 1 treats wpa psk as
+        encoded passphrase. You can generate an encoded passphrase with
+        the wpa\_passphrase utility. This is especially useful if your
+        passphrase contains special characters. This option only works
+        when using mac80211 or atheros type devices.
+
     \item \texttt{server} (wpa) \\
         The RADIUS server ip address