ARM: dts: Add #address-cells & #size-cells to gpu-pwrlevels node

gpu-pwrlevel@ node reg values are a single uint32 that represent the
address with no size field. Set #address-cells=1 and #size-cells=0
to fix the build warnings messages.

Change-Id: Ib0339ddbde32a8a360ac721f0387b4317e5e9455
Signed-off-by: Hareesh Gundu <hareeshg@codeaurora.org>