scripts/dtc: Re-sync with Linux 4.17-rc4

To achieve a DTC state (more or less) equivalent to Linux 4.17-rc4,
backport the DTC-specific part from below Linux commits:

b23d1a241f4eb4 ("kbuild: add %.lex.c and %.tab.[ch] to 'targets' automatically")
9a8dfb394c0467 ("kbuild: clean up *.lex.c and *.tab.[ch] patterns from top-level Makefile")
59889300274569 (".gitignore: move *.lex.c *.tab.[ch] patterns to the top-level .gitignore")
e039139be8c251 ("scripts/dtc: generate lexer and parser during build instead of shipping")
b24413180f5600 ("License cleanup: add SPDX GPL-2.0 license identifier to files with no license")

With this commit, the diff between Linux and U-boot common DTC files is:
$ git diff --stat --diff-filter=M v4.17-rc4 <this-commit> -- scripts/dtc
  scripts/dtc/.gitignore | 2 +-
  scripts/dtc/Makefile   | 3 +++

The delta is coming from U-boot commits:
* v2017.11 de163ecedb ("scripts: dtc: Add .gitignore")
* v2018.01 15b97f5c5e ("pylibfdt: move pylibfdt to scripts/dtc/pylibfdt and refactor makefile")

Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/dtc/update-dtc-source.sh

@@ -1,9 +1,10 @@
 #!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
 # Simple script to update the version of DTC carried by the Linux kernel
 #
 # This script assumes that the dtc and the linux git trees are in the
 # same directory. After building dtc in the dtc directory, it copies the
-# source files and generated source files into the scripts/dtc directory
+# source files and generated source file(s) into the scripts/dtc directory
 # in the kernel and creates a git commit updating them to the new
 # version.
 #
@@ -33,7 +34,6 @@ DTC_LINUX_PATH=`pwd`/scripts/dtc
 DTC_SOURCE="checks.c data.c dtc.c dtc.h flattree.c fstree.c livetree.c srcpos.c \
 		srcpos.h treesource.c util.c util.h version_gen.h Makefile.dtc \
 		dtc-lexer.l dtc-parser.y"
-DTC_GENERATED="dtc-lexer.lex.c dtc-parser.tab.c dtc-parser.tab.h"
 LIBFDT_SOURCE="Makefile.libfdt fdt.c fdt.h fdt_addresses.c fdt_empty_tree.c \
 		fdt_overlay.c fdt_ro.c fdt_rw.c fdt_strerror.c fdt_sw.c \
 		fdt_wip.c libfdt.h libfdt_env.h libfdt_internal.h"
@@ -58,10 +58,6 @@ for f in $DTC_SOURCE; do
 	cp ${DTC_UPSTREAM_PATH}/${f} ${f}
 	git add ${f}
 done
-for f in $DTC_GENERATED; do
-	cp ${DTC_UPSTREAM_PATH}/$f ${f}_shipped
-	git add ${f}_shipped
-done
 for f in $LIBFDT_SOURCE; do
        cp ${DTC_UPSTREAM_PATH}/libfdt/${f} libfdt/${f}
        git add libfdt/${f}