timekeeping: Introduce tkd_basic_setup() to make lock and seqcount init reusable

timekeeping: Introduce tkd_basic_setup() to make lock and seqcount init reusable

Initialization of lock and seqcount needs to be done for every instance of
timekeeper struct. To be able to easily reuse it, create a separate
function for it.

Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-11-554456a44a15@linutronix.de