dt-bindings: cpu: Drop duplicate nvidia,tegra186-ccplex-cluster.yaml

"nvidia,tegra186-ccplex-cluster" is also documented in
arm/tegra/nvidia,tegra-ccplex-cluster.yaml. As it covers Tegra234 as
well, drop nvidia,tegra186-ccplex-cluster.yaml.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240910234422.1042486-1-robh@kernel.org
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>