dt-bindings: rockchip: grf: Add missing type to 'pcie-phy' node

'pcie-phy' is missing any type. Add 'type: object' to indicate it's a
node.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240401204959.1698106-1-robh@kernel.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>