perf jevents.py: Make generated C code more kernel style

perf jevents.py: Make generated C code more kernel style

Make jevents.py generate C code that complies with formatting tools:

- Add /* clang-format off */ before big_c_string and re-enable it
  after system mapping tables, bypassing large generated tables while
  checking functions and early structs.
- Make comments more human readable and avoid going over 100 character
  line length.
- Fix spaces indentation to tabs in struct/array initializers.
- Fix other checkpatch detected related issues.

Assisted-by: Gemini-CLI:Google Gemini 3
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>