kernel: bump 4.9 to 4.9.117 for 18.06

kernel: bump 4.9 to 4.9.117 for 18.06

* Refreshed patches.
* Removed patches:
  - target/linux/ar71xx/patches-4.9/103-MIPS-ath79-fix-register-address-in-ath79_ddr_wb_flus.patch superseded by upstream
  - target/linux/ar71xx/patches-4.9/403-mtd_fix_cfi_cmdset_0002_status_check.patch superseded by upstream
  - target/linux/brcm63xx/patches-4.9/001-4.11-01-mtd-m25p80-consider-max-message-size-in-m25p80_read.patch accepted upstream
  - target/linux/brcm63xx/patches-4.9/001-4.15-08-bcm63xx_enet-correct-clock-usage.patch accepted upstream
  - target/linux/brcm63xx/patches-4.9/001-4.15-09-bcm63xx_enet-do-not-write-to-random-DMA-channel-on-B.patch accepted upstream
  - target/linux/generic/pending-4.9/900-gen_stats-fix-netlink-stats-padding.patch

* New backported patch to address ext4 breakage, introduced in 4.9.112:
  - backport-4.9/500-ext4-fix-check-to-prevent-initializing-reserved-inod.patch

Also add ARM64_SSBD symbol to ARM64 targets still running kernel 4.9

Thanks to Koen Vandeputte for pointing out the need to add the ARM64_SSBD symbol, and the ext4 patch.

Compile-tested on: ar71xx
Run-tested on: ar71xx

Signed-off-by: Stijn Segers <foss@volatilesystems.org>