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>

SVN-Revision: 41998