msm: kgsl: Do not request_mem_region for GMU

The register range that is being mapped by the GMU
will be changed to include a range that is already
requested by the clock driver. Only remap during
probe so that there are no conflicts when the
range is changed.

CRs-Fixed: 2017390
Change-Id: Iaf9ad769d0ebfd56ba8d375db62f9942b017fc68
Signed-off-by: Kyle Piefer <kpiefer@codeaurora.org>