cpufreq: schedutil: Rework the fast switch limits logic

Due to certain misunderstandings about the workings of the cpufreq driver,
the original fast switch logic had several bugs in place. Instead of
creating multiple changes to address them, redesign the fast switch limits
code properly.

Change-Id: I8eb8835d63ecd4ae6c6b406a8e2b33409e856a80
Signed-off-by: Jonathan Avila <avilaj@codeaurora.org>