cpufreq: bring in minmax governor

 * CREDITS to @Erasmux
 * I loved this one on my TF101, revive it.
 * Rewritten for new cpufreq API

Signed-off-by: Luis Cruz <ljc2491@gmail.com>
Signed-off-by: Dan Trifan <jimsth@gmail.com>
defconfig: updates for MINMAX cpu governor

Signed-off-by: Dan Trifan <jimsth@gmail.com>