Revert "increase l2 speed and slightly cpu undervolt"

This reverts commit 353134e9ebbbb9fb2b0c84e045709c371d6e251d.
msm: kgsl: Allow GPU start to run in a high priority queue -- Thanks to @mrg666
Rework about L2 bus speed optimization
Lower Min Brightness
build & config updates
Increase touch UI response Thanks @faux123