dt-bindings: net: mediatek,net: add sram property

dt-bindings: net: mediatek,net: add sram property

Meditak Filogic SoCs (MT798x) have dedicated MMIO-SRAM for dma operations.

MT7981 and MT7986 currently use static offset to ethernet MAC register
which will be changed in separate patch once this way is accepted.

Add "sram" property to map ethernet controller to dedicated mmio-sram node.

Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20250709111147.11843-5-linux@fw-web.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>