KGSL: make simple govenor a selectable option, co-exist with ondemand

also removed some hardcoded values

Signed-off-by: Paul Reioux <reioux@gmail.com>

Conflicts:
	drivers/gpu/msm/kgsl_pwrscale_trustzone.c
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>