kernel: bump 4.14 to 4.14.20

Refresh patches.
Remove upstreamed patches:
- backport/080-v4.15-0001-arch-define-weak-abort.patch
- backport/081-v4.15-0002-kernel-exit.c-export-abort-to-modules.patch
Update patch that no longer applies:
pending/493-ubi-set-ROOT_DEV-to-ubiblock-rootfs-if-unset.patch

Fixes CVE-2017-8824.

Compile-tested: octeon, x86/64.
Runtime-tested: octeon, x86/64.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>

target/linux/ramips/patches-4.14/0040-nand-hack.patch

@@ -18,7 +18,7 @@
  			if (ret < 0) {
  				if (use_bufpoi)
  					/* Invalidate page cache */
-@@ -3076,8 +3080,11 @@ int nand_erase_nand(struct mtd_info *mtd
+@@ -3079,8 +3083,11 @@ int nand_erase_nand(struct mtd_info *mtd
  		    (page + pages_per_block))
  			chip->pagebuf = -1;
  
@@ -31,7 +31,7 @@
  		/* See if block erase succeeded */
  		if (status & NAND_STATUS_FAIL) {
  			pr_debug("%s: failed erase, page 0x%08x\n",
-@@ -4207,6 +4214,7 @@ int nand_scan_ident(struct mtd_info *mtd
+@@ -4210,6 +4217,7 @@ int nand_scan_ident(struct mtd_info *mtd
  		 * cmdfunc() both expect cmd_ctrl() to be populated,
  		 * so we need to check that that's the case
  		 */