arm64: dts: mediatek: mt7986a: bpi-r3: Convert to sugar syntax

Overlay syntactic sugar for generating target-path fragments is
supported by the version of dtc supplied with the kernel since commit
50aafd60 ("scripts/dtc: Update to upstream version
v1.4.6-21-g84e414b0b5bc").  Hence convert the Bananapi R3 overlay
devicetree source files to sugar syntax, improving readability.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/2fd900a30b5a0f7de4ea68f60bac250794b8cdb4.1716984213.git.geert+renesas@glider.be


Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>