scripts/dtc: Update to upstream version v1.6.1-66-gabbd523bae6e

This adds the following commits from upstream:

abbd523bae6e pylibfdt: Work-around SWIG limitations with flexible arrays
a41509bea3e7 libfdt: Replace deprecated 0-length arrays with proper flexible arrays
2cd89f862cdb dtc: Warning rather than error on possible truncation of cell values

Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/all/20230203172430.474431-1-robh@kernel.org/


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