arm64: dts: mediatek: mt8195: Add SCP phandle to MDP3 DMA controller

arm64: dts: mediatek: mt8195: Add SCP phandle to MDP3 DMA controller

While the MDP3 DMA controller can look for the SCP node based on
compatible, it's best practice to supply the MDP3 node with a phandle to
the SCP since that allows supporting dual core SCP as well. Besides,
relying on the compatible search causes an error to be printed, since
the phandle is tried first:

  mtk-mdp3 14001000.dma-controller: can't get SCP node

Add the missing phandle to follow the best practice and get rid of the
error.

Fixes: 5710462a116c ("arm64: dts: mediatek: mt8195: add MDP3 nodes")
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Link: https://lore.kernel.org/r/20240606-mt8195-dma-scp-node-err-v2-1-e14702e9d3f2@collabora.com
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>