cpufreq_conservative: Reduce minimum polling interval

Conservative's minimum polling interval is very long - this patch reduces
it so the user can tune it downwards, while still respecting hardware
transition_latency limits.

Signed-off-by: Andrew Dodd <atd7@cornell.edu>
cpufreq_conservative: Change default tuning settings

Half the polling rate, but more aggressive up/down thresholds.

Signed-off-by: Andrew Dodd <atd7@cornell.edu>
cpufreq_conservative: Bump default frequency step up to 10 from 5

Based on a better understanding of how the governor operates,
this is a better choice on most Exynos devices.

Change-Id: I8ed87e2b61f621138aa5a20951d8a70037e986a9
Signed-off-by: Andrew Dodd <atd7@cornell.edu>
config: Enable conservative governor

Change-Id: I53b96ab35138c9d82bec31e0782a34d9e29fce5c