rtc: fix inverted resolution check

[royger]

Summary

The current code in clock_register checks if the newly added clock has a
resolution value higher than the current one in order to make it the
default, which is wrong. Clocks with a lower resolution value should be
better than ones with a higher resolution value, in fact with the current
code FreeBSD is always selecting the worse clock.

Sponsored by: Citrix Systems R&D

[kib]

Was it dormant because typical system is x86 with only one RTC clock ?

[jhb]

It's also kind of "backwards" (like thread priorities) where a numerically lower value means "higher" precision (i.e. more precise). Given the text in the printf I think it's easy to get the expression wrong.

[royger]

In D6185#131704, @kib wrote:

Was it dormant because typical system is x86 with only one RTC clock ?

AFAICT yes, most platforms only have one clock available, so this bug has never surfaced.

Thanks all for the review.