arm64/rk805: remove RTC Set logging

When ntpd is synchronizing the system time, it also periodically (30m)
syncs the the RTC time. Remove printf in rk805_settime which triggers
every 30m, as settime_task_func() will log errors under bootverbose.
We leave the RTC Read logging, which should happen only once at boot.

Commit message by: imp
Reviewed by: manu, imp
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D30361