cpufreq: cpu-boost: Increase sync thread policy and priority

More or less all cpufreq related threads run in a high priority.

Also, CMs patch series was somehow out of sync and incomplete,
readd the unchanged policy update to source cpu bit. And readd
the check for a possible corner case in try_to_wake_up() that
was already missing before.

Signed-off-by: revjunkie <gadgetjuan@gmail.com>