msm: kgsl: Enable IO coherency for A615 and A616 GPU

Enable ADRENO_IOCOHERENT feature flag for A615 and
A616 GPUs to enable IO coherency support. This allow
userspace to mark a buffer as IO coherent.

Change-Id: Ifef3982261fca79e7d0ebe5ab5f0c343d8d9feb8
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>