atheros: upgrade to 2.6.28 by default

SVN-Revision: 14985

target/linux/atheros/Makefile

@@ -11,7 +11,7 @@ BOARD:=atheros
 BOARDNAME:=Atheros 231x/5312
 FEATURES:=squashfs jffs2
 
-LINUX_VERSION:=2.6.26.8
+LINUX_VERSION:=2.6.28.7
 
 include $(INCLUDE_DIR)/target.mk