ARM: dts: msm: disable kgsl-smmu test device node on msm8953

Disable test device node added against graphics SMMU which otherwise
causes conflicts with the original usecase device node.

Change-Id: I41db17ffa135f1cf232fb63f8a66b05b9c59ebba
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>