scripts/dtc: Update to upstream version v1.6.1-19-g0a3a9d3449c8

This adds the following commits from upstream:

0a3a9d3449c8 checks: Add an interrupt-map check
8fd24744e361 checks: Ensure '#interrupt-cells' only exists in interrupt providers
d8d1a9a77863 checks: Drop interrupt provider '#address-cells' check
52a16fd72824 checks: Make interrupt_provider check dependent on interrupts_extended_is_cell
37fd700685da treesource: Maintain phandle label/path on output
e33ce1d6a8c7 flattree: Use '\n', not ';' to separate asm pseudo-ops
d24cc189dca6 asm: Use assembler macros instead of cpp macros
ff3a30c115ad asm: Use .asciz and .ascii instead of .string
5eb5927d81ee fdtdump: fix -Werror=int-to-pointer-cast
0869f8269161 libfdt: Add ALIGNMENT error string
69595a167f06 checks: Fix bus-range check
72d09e2682a4 Makefile: add -Wsign-compare to warning options
b587787ef388 checks: Fix signedness comparisons warnings
69bed6c2418f dtc: Wrap phandle validity check
910221185560 fdtget: Fix signedness comparisons warnings
d96...