Do not read the status MSR before setting performance adjustment mode.

Do not read the status MSR before setting performance adjustment mode.
This makes modifying hw.setperf and apmd -A work on robert's laptop.
Previously, it would sometimes be impossible to set hw.setperf to any
value on this machine.

Keep a delay loop that waits for the MSR write to take effect before
setting hw.cpuspeed to the new value since this is apparently needed
for some pre-ryzen processors.

Debugging, initial diff & test by robert

ok brynet