port-arm/57139: CPU frequency setting does not seem to work on Raspberry Pi 4

[cryintothebluesky%gmail.com@localhost]

>Number:         57139
>Category:       port-arm
>Synopsis:       CPU frequency setting does not seem to work on Raspberry Pi 4
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-arm-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Dec 27 21:00:01 +0000 2022
>Originator:     Sad Clouds
>Release:        10.0_BETA
>Organization:
>Environment:
NetBSD rp4-netbsd 10.0_BETA NetBSD 10.0_BETA (GENERIC64) #0: Fri Dec 23 11:21:46 GMT 2022
>Description:
Setting CPU frequency to 600 does not seem to be supported, as the current frequency is still reported as 1500

# sysctl -w machdep.cpu.frequency.target=600
machdep.cpu.frequency.target: 1500 -> 600

# sysctl machdep.cpu.frequency
machdep.cpu.frequency.target = 1500
machdep.cpu.frequency.current = 1500
machdep.cpu.frequency.min = 600
machdep.cpu.frequency.max = 1500
machdep.cpu.frequency.available = 600 1500

>How-To-Repeat:

>Fix: