Request GPU Voltage setting

[shumashv1]

A feature for various kernels allows setting of the GPU voltages. A reference to my specific commit is: https://github.com/shumashv1/android_kernel-3.4_hp_tenderloin/commit/57ec2123b6b3f4a3db4c0bfc97fa194b35e7852d

Some other commits have changed the attribute group from "vddtbl" to "voltage", but I haven't to keep it consistent with KA.

An app from alaskalinuxsuser implements setting the GPU voltage for the S4.

Could you add this capability to KA?