posix-timers: Polish coding style in a few places

Make it consistent with the TIP tree documentation.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230425183313.888493625@linutronix.de