drivers: cpufreq: Initialize governors earlier

Initialize cpufreq governors earlier so we can run at the highest
frequencies sooner during boot (in case the bootloader programmed a
conservative frequency) and conversely throttle back earlier too in case
thermal mitigation is needed.

Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Ondrej Kubik <ondrej.kubik@canonical.com>