Fix config.in typo and enable by default only for ixp4xx-2.6

SVN-Revision: 7458

target/linux/ixp4xx-2.6/image/Config.in

@@ -1,6 +1,6 @@
 config IXP4XX_INCLUDE_UCODE
-	bool "Build images with Intel IXP4xx Microcode
-	default y
+	bool "Build images with Intel IXP4xx Microcode"
+	default y if LINUX_2_6_IXP4XX
 	help
 	  You must manually download IPL_ixp400NpeLibrary-2_4.zip from
 	  http://www.intel.com/design/network/products/npfamily/ixp400_archives.htm