scripts/dtc: Update to upstream version v1.5.1-22-gc40aeb60b47a

This adds the following commits from upstream:

c40aeb60b47a travis.yml: Run tests on the non-x86 builders, too
9f86aff444f4 Add .cirrus.yml for FreeBSD build
34c82275bae6 Avoid gnu_printf attribute when using Clang
743000931bc9 tests: default to 'cc' if CC not set
adcd676491cc Add test-case for trailing zero
d9c55f855b65 Remove trailing zero from the overlay path
7a22132c79ec pylibfdt: Adjust for deprecated test methods
dbe80d577ee2 tests: add extension to sed -i for GNU/BSD sed compatibility
af57d440d887 libfdt: Correct prototype for fdt_ro_probe_()
6ce585ac153b Use correct inttypes.h format specifier
715028622547 support byacc in addition to bison
fdf3f6d897ab pylibfdt: Correct the type for fdt_property_stub()
430419c28100 tests: fix some python warnings
588a29ff2e4e util: use gnu_printf format attribute
bc876708ab1d fstree: replace lstat with stat
4c3c4ccb9916 dumptrees: pass outputdir as first argument
aa522da9fff6 tests: allow out-of-tr...