portability: Remove C99-illegal semicolons from the global scope

This commit touches the C codebase and the python syscall generator.

The Z_GENLIST-macros expand to whole functions. Once expanded by the
preprocessor we notice a semicolon is put after the function body. But
ISO C99 does not allow extra ‘;’ outside of a function. Though this is
accepted by GCC with GNU extensions, it is not by Clang.

Signed-off-by: Mark Ruvald Pedersen <mped@oticon.com>