msm: kgsl: Check GX status before enabling / disabling

Check to see that GX is not already in the wanted state
before putting it in that state.

CRs-Fixed: 2017390
Change-Id: I369858b1da170503c79869f5d45711d079cfe397
Signed-off-by: Kyle Piefer <kpiefer@codeaurora.org>