msm: kgsl: Add the hwsched platform driver

This adds the skeleton for the hwsched driver to be
used for dispatching submissions using hwscheduling.

Change-Id: I963fe6b16deb58edab78ab0e9c66fae0d9294b9a
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>