Changed description of upgrade function in WebUI

Flashing of stock firmware is different for different devices.
At least on TP-Link Images it's not working via sysupgrade.

Signed-off-by: Jan Kraus <mayosemmel@gmail.com>
Reviewed-by: Christian Dresel <fff@chrisi01.de>
Reviewed-by: Tim Niemeyer <tim@tn-x.org>

src/packages/fff/fff-web/files/www/ssl/cgi-bin/upgrade.html

@@ -42,7 +42,7 @@ fi
 		<tr><th>Konfiguration&nbsp;erhalten:</th><td><input type="checkbox" name="keep_config" checked /></td></tr>
 		<tr><td colspan="2"><input type="submit" name="upgrade" value="Upgrade" /></td></tr>
 		<tr><td colspan="2"></td></tr>
-		<tr><td colspan="2">Hier kann ein Freifunk-Image verwendet werden (*-sysupgrade.bin) oder die Firmware des Routerherstellers.</td></tr>
+		<tr><td colspan="2">Hier kann ein Freifunk- oder OpenWRT-Image verwendet werden (*-sysupgrade.bin).</td></tr>
 	</table>
 </fieldset>
 </td><td>