hrtimers: Switch to use __htimer_setup()

__hrtimer_init_sleeper() calls __hrtimer_init() and also sets up the
callback function. But there is already __hrtimer_setup() which does both
actions.

Switch to use __hrtimer_setup() to simplify the code.

Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/all/d9a45a51b6a8aa0045310d63f73753bf6b33f385.1738746927.git.namcao@linutronix.de