gre: Change hostdependcy to remote endpoint tunnel address

Depend on the GRE tunnel peeraddr to trigger setup of the tunnel interface.
Addresses the issue reported in https://lists.openwrt.org/pipermail/openwrt-devel/2014-August/027201.html



Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

git-svn-id: svn://svn.openwrt.org/openwrt/branches/barrier_breaker@41999 3c298f89-4303-0410-b956-a3cf2f4a3e73