ARM: dts: rockchip: Fix gpu opp node names for rk3288

[ Upstream commit d040e4e8 ]

The device tree compiler yells like this:
  Warning (unit_address_vs_reg):
  /gpu-opp-table/opp@100000000:
  node has a unit name, but no reg property

Let's match the cpu opp node names and use a dash.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>