ppp: add more pppol2tpv3 related structs from the kernel headers to fix...

ppp: add more pppol2tpv3 related structs from the kernel headers to fix compile issues with linux 3.6

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@34070 3c298f89-4303-0410-b956-a3cf2f4a3e73