cpufreq: interactive: rework suspend/resume logic

Complete rework of the suspend/resume logic.
This is how it works now;

 * If the device screen goes off, the frequency will
   be changed to the preconfigured suspend_freq.

 * This new suspend_freq is completely configurable
   /sys/devices/system/cpu/cpufreq/interactive/suspend_freq
   (default is 300 MHz)

 * If the device screen goes on, it will be instantly
   boosted to the input_boost_freq (1 GHz), to avoid
   any possible lag

 * Also suspend_enabled is on by default back again.

 * No hack is longer required for the speedchange_task.
   Just a simple flag will handle everything.
   This fixes also the bug where no other governor
   could be selected after interactive had its first
   sleep.

 * No more barrier-code to check if there is some load.

Signed-off-by: Blechd0se <alex.christ@hotmail.de>