lantiq: copy target to kernel 5.4

Duplicate kernel 4.19 config and patches for kernel 5.4.

Duplicate the devicetree source files as well, they need kernel 5.4
specific adjustments.

Signed-off-by: Mathias Kresin <dev@kresin.me>

target/linux/lantiq/patches-5.4/0042-arch-mips-increase-io_space_limit.patch

@@ -0,0 +1,23 @@
+From 9807eb80a1b3bad7a4a89aa6566497bb1cadd6ef Mon Sep 17 00:00:00 2001
+From: John Crispin <john@phrozen.org>
+Date: Fri, 3 Jun 2016 13:12:20 +0200
+Subject: [PATCH] arch: mips: increase io_space_limit
+
+this value comes from x86 and breaks some pci devices
+
+Signed-off-by: John Crispin <john@phrozen.org>
+---
+ arch/mips/include/asm/io.h |    2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- a/arch/mips/include/asm/io.h
++++ b/arch/mips/include/asm/io.h
+@@ -52,7 +52,7 @@
+ 
+ /* ioswab[bwlq], __mem_ioswab[bwlq] are defined in mangle-port.h */
+ 
+-#define IO_SPACE_LIMIT 0xffff
++#define IO_SPACE_LIMIT 0xffffffff
+ 
+ /*
+  * On MIPS I/O ports are memory mapped, so we access them using normal