kernel: generic: Add kernel 4.14 support

This adds initial support for kernel 4.14 based on the patches for
kernel 4.9.

In the configuration I deactivated some of the new possible security
features like:
CONFIG_REFCOUNT_FULL
CONFIG_SLAB_FREELIST_HARDENED
CONFIG_SOFTLOCKUP_DETECTOR
CONFIG_WARN_ALL_UNSEEDED_RANDOM

And these overlay FS options are also deactivated:
CONFIG_OVERLAY_FS_INDEX
CONFIG_OVERLAY_FS_REDIRECT_DIR

I activated this:
CONFIG_FORTIFY_SOURCE
CONFIG_POSIX_TIMERS
CONFIG_SLAB_MERGE_DEFAULT
CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED

I am not sure if I did the porting correct for the following patches:
target/linux/generic/backport-4.14/020-backport_netfilter_rtcache.patch
target/linux/generic/hack-4.14/220-gc_sections.patch
target/linux/generic/hack-4.14/321-powerpc_crtsavres_prereq.patch
target/linux/generic/pending-4.14/305-mips_module_reloc.patch
target/linux/generic/pending-4.14/611-netfilter_match_bypass_default_table.patch
target/linux/generic/pending-4.14/680-NET-skip-GRO-for-foreign-MAC-addresses.patch

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

target/linux/generic/pending-4.14/616-net_optimize_xfrm_calls.patch

@@ -0,0 +1,20 @@
+From: Felix Fietkau <nbd@nbd.name>
+Subject: kernel: add a small xfrm related performance optimization
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+ net/netfilter/nf_nat_core.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+--- a/net/netfilter/nf_nat_core.c
++++ b/net/netfilter/nf_nat_core.c
+@@ -90,6 +90,9 @@ int nf_xfrm_me_harder(struct net *net, s
+ 	struct dst_entry *dst;
+ 	int err;
+ 
++	if (skb->dev && !dev_net(skb->dev)->xfrm.policy_count[XFRM_POLICY_OUT])
++		return 0;
++
+ 	err = xfrm_decode_session(skb, &fl, family);
+ 	if (err < 0)
+ 		return err;