dt-bindings: arm64: mediatek: add BananaPi R3 Mini

Add MT7988A based BananaPi R3 Mini.
Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20240510095707.6895-2-linux@fw-web.deSigned-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Documentation/devicetree/bindings/arm/mediatek.yaml

@@ -92,6 +92,7 @@ properties:
           - enum:
               - acelink,ew-7886cax
               - bananapi,bpi-r3
+              - bananapi,bpi-r3mini
               - mediatek,mt7986a-rfb
           - const: mediatek,mt7986a
       - items: