ath79: add support for kernel 5.4

Signed-off-by: David Bauer <mail@david-bauer.net>
[refreshed]
Signed-off-by: Koen Vandeputte <koen.vandeputte@ncentric.com>

* Sync the patches with the changes done for kernel 4.19
* Use KERNEL_TESTING_PATCHVER
* Refresh the configuration
* Fix multiple compile bugs in the patches
* Only add own ag71xx files for kernel 4.19 and use upstream version for
  5.4.

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

target/linux/ath79/patches-5.4/405-mtd-tp-link-partition-parser.patch

@@ -0,0 +1,25 @@
+--- a/drivers/mtd/Kconfig
++++ b/drivers/mtd/Kconfig
+@@ -62,6 +62,12 @@ config MTD_MYLOADER_PARTS
+ 	  You will still need the parsing functions to be called by the driver
+ 	  for your particular device. It won't happen automatically.
+ 
++config MTD_TPLINK_PARTS
++	tristate "TP-Link AR7XXX/AR9XXX partitioning support"
++	depends on ATH79
++	---help---
++	  TBD.
++
+ comment "User Modules And Translation Layers"
+ 
+ #
+--- a/drivers/mtd/Makefile
++++ b/drivers/mtd/Makefile
+@@ -8,6 +8,7 @@ obj-$(CONFIG_MTD)		+= mtd.o
+ mtd-y				:= mtdcore.o mtdsuper.o mtdconcat.o mtdpart.o mtdchar.o
+ 
+ obj-y				+= parsers/
++obj-$(CONFIG_MTD_TPLINK_PARTS)	+= tplinkpart.o
+ 
+ # 'Users' - code which presents functionality to userspace.
+ obj-$(CONFIG_MTD_BLKDEVS)	+= mtd_blkdevs.o