msm: kgsl: Remove the isense enablement function

Remove most of the current sensor register accesses
from the kgsl driver as they are moved to the GMU
firmware.

Change-Id: Ifc180e8358b4ea12249755cf6294d191b4f61bf7
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>