kernel: add missing check for skb->dev on netfilter xfrm optimization patch

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@43567 3c298f89-4303-0410-b956-a3cf2f4a3e73
kernel: backport an upstream xfrm crash fix

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@43568 3c298f89-4303-0410-b956-a3cf2f4a3e73
kernel: update linux 3.18 to final release

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@43569 3c298f89-4303-0410-b956-a3cf2f4a3e73