arm64: dts: mediatek: mt7988a-bpi-r4: add sfp cages and link to gmac

Add SFP cages to Bananapi-R4 board. The 2.5g phy variant only contains the
wan-SFP, so add this to common dtsi and the lan-sfp only to the dual-SFP
variant.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20250709111147.11843-13-linux@fw-web.de


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>