scripts/dtc: Update to upstream version v1.6.0-51-g183df9e9c2b9

This adds the following commits from upstream:

183df9e9c2b9 gitignore: Ignore the swp files
0db6d09584e1 gitignore: Add cscope files
307afa1a7be8 Update Jon Loeliger's email
ca16a723fa9d fdtdump: Fix gcc11 warning
64990a272e8f srcpos: increase MAX_SRCFILE_DEPTH
163f0469bf2e dtc: Allow overlays to have .dtbo extension
3b01518e688d Set last_comp_version correctly in new dtb and fix potential version issues in fdt_open_into
f7e5737f26aa tests: Fix overlay_overlay_nosugar test case
7cd5d5fe43d5 libfdt: Tweak description of assume-aligned load helpers
a7c404099349 libfdt: Internally perform potentially unaligned loads
bab85e48a6f4 meson: increase default timeout for tests
f8b46098824d meson: do not assume python is installed, skip tests
30a56bce4f0b meson: fix -Wall warning
5e735860c478 libfdt: Check for 8-byte address alignment in fdt_ro_probe_()
67849a327927 build-sys: add meson build
05874d08212d pylibfdt: allow build out of tree
3bc3a6b9fe0c dtc: Fix signedness comparisons warnings: Wrap (-1)
e1147b159e92 dtc: Fix signedness comparisons warnings: change types
04cf1fdc0fcf convert-dtsv0: Fix signedness comparisons warning
b30013edb878 libfdt: Fix kernel-doc comments

Signed-off-by: Rob Herring <robh@kernel.org>