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-4.14/206-mips-disable-vdso.patch

@@ -0,0 +1,23 @@
+From: Felix Fietkau <nbd@nbd.name>
+Subject: kernel: disable MIPS VDSO by default until the cache issues have been resolved
+
+lede-commit: 1185e645a773c86aa88cf04d0e2911dc62eb43f5
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+ arch/mips/vdso/Makefile | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+--- a/arch/mips/vdso/Makefile
++++ b/arch/mips/vdso/Makefile
+@@ -30,9 +30,9 @@ aflags-vdso := $(ccflags-vdso) \
+ ifndef CONFIG_CPU_MIPSR6
+   ifeq ($(call ld-ifversion, -lt, 225000000, y),y)
+     $(warning MIPS VDSO requires binutils >= 2.25)
+-    obj-vdso-y := $(filter-out gettimeofday.o, $(obj-vdso-y))
+-    ccflags-vdso += -DDISABLE_MIPS_VDSO
+   endif
++  obj-vdso-y := $(filter-out gettimeofday.o, $(obj-vdso-y))
++  ccflags-vdso += -DDISABLE_MIPS_VDSO
+ endif
+ 
+ # VDSO linker flags.