uc-def generates truncated headers with recent Python versions

With recent Python versions, e.g. Python 3.12, the uc-def script may generate truncated headers. Building with make V=1 reveals a Python warning:

./scripts/uc-def/uc-def:240: SyntaxWarning: "is not" with 'str' literal. Did you mean "!="?

Steps to reproduce

Clone the DirtyJTAG repo (https://github.com/dirtyjtag/DirtyJTAG) and try to build with make. It will raise missing #endif errors in a generated generated header. Build with make V=1 to get the aforementioned Python warning.

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