checkpatch: update from Linux v4.13-rc6

Checkpatch produces the following warning:

Unescaped left brace in regex is deprecated here
(and will be fatal in Perl 5.30), passed through in regex;
marked by <-- HERE in m/^(\+.*(?:do|\))){ <-- HERE /
at scripts/checkpatch.pl line 3348.

The curent checkpatch of the Linux kernel corrects this
bug and many others.

It provides improved colored output.

So replace checkpatch by the current Linux version.

Add an empty file scripts/const_structs.checkpatch.
We can later fill it according to our needs.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

scripts/const_structs.checkpatch

@@ -0,0 +1,2 @@
+# Put structs here that should be constant
+__dummy__