KGSL: Add a simple GPU governor for Adreno xxx GPU series

initial coding for a Simple GPU governor based on my own work 2 years ago
from Sensation GB kernel commit: c1ea8f64167270d67915b4d4fb00910b1c0f513f

Signed-off-by: Paul Reioux <reioux@gmail.com>
KGSL: make simple govenor a selectable option, co-exist with ondemand

also removed some hardcoded values

Signed-off-by: Paul Reioux <reioux@gmail.com>
KGSL: simple governor: expose tunables to sysfs interface via module_param

Signed-off-by: Paul Reioux <reioux@gmail.com>
KGSL: Simple Governor: fix minor logic issue

Signed-off-by: Paul Reioux <reioux@gmail.com>
defconfig: enable simple govenor for gpu

Change-Id: I160f43940d24c296643b6fc6ed449604fa0b8355
drivers/gpu/msm/kgsl_pwrscale_trustzone.c: fixed warning: 'idle' may be
used uninitialized in this function [-Wmaybe-uninitialized]

Change-Id: If3625d610244b30322a00a50a568995317148ff9