msm: kgsl: no need to cast long because jiffies and window_time are already long.

Change-Id: I5f45ecf2c2b95f289c9ac4e62af16c032086be27
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
msm: kgsl: change the load calculation equation & fix a couple of bugs, one of 'em was keeping the GPU on 320MHz if the GPU was not sleeping.

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>

Change-Id: Iaa4eacf3a1351519c25ec1f01c2fc3f472d43c6a