BugLink: http://bugs.launchpad.net/bugs/1573034

[ Upstream commit 6faac63a ]

Add missing rtnl_unlock() in the error path of ppp_create_interface().

Fixes: 58a89eca ("ppp: fix lockdep splat in ppp_dev_uninit()")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>