realtek: timer: Register enabled scheduler clock

realtek: timer: Register enabled scheduler clock

Before calling sched_clock_register(), the timer used to drive the
scheduling clock should already be enabled. Otherwise the kernel log
will show strange time jumps during, and the watchdog might not be
pinged in a timely fashion, resulting in reboots.

[    0.160281] NET: Registered PF_NETLINK/PF_ROUTE protocol family
[   78.104319] clocksource: Switched to clocksource realtek_otto_timer

Fixes: 3cc801117118 ("realtek: resurrect timer driver")
Signed-off-by: Sander Vanheule <sander@svanheule.net>