Default to CONFIG_LMB_LIMIT_DMA_BELOW_RAM_TOP=y when MEDIATEK_ETH is enabled. The MediaTek Ethernet controller can only access the first 4GB of RAM when DMA is used. Link: https://patch.msgid.link/20260615-mtk-fix-ram-size-v2-2-f72cfc52ce58@baylibre.com Signed-off-by: David Lechner <dlechner@baylibre.com>