target/tricore: Rename csfr.def -> csfr.h.inc

We use the .h.inc extension to include C headers. To be consistent
with the rest of the codebase, rename the C headers using the .def
extension.

IDE/tools using our .editorconfig / .gitattributes will leverage
this consistency.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20221025235006.7215-4-philmd@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>