db: remove unused ethernetPorts option

intel_mips/README.md

intel_mips/base-files/etc/board-db/boards/EASY350

intel_mips/base-files/etc/board-db/boards/EASY550

intel_mips/base-files/etc/board-db/boards/NORRLAND

intel_mips/base-files/etc/board-db/boards/SPEEDPORT_SMART3

iopsys-armvirt/base-files/etc/board-db/boards/ARMVIRT

...rcm63xx-arm/base-files/etc/board-db/boards/963138REF_P502

...rcm63xx-arm/base-files/etc/board-db/boards/963138REF_P802

iopsys-brcm63xx-arm/base-files/etc/board-db/boards/96752REF1

...rcm63xx-arm/base-files/etc/board-db/boards/968580XREF_PHY

...-brcm63xx-arm/base-files/etc/board-db/boards/DG400PRIMER0

iopsys-brcm63xx-arm/base-files/etc/board-db/boards/E600

iopsys-brcm63xx-arm/base-files/etc/board-db/boards/EX600

iopsys-brcm63xx-arm/base-files/etc/board-db/boards/FT_G6416

iopsys-brcm63xx-arm/base-files/etc/board-db/boards/FT_G6426

iopsys-brcm63xx-arm/base-files/etc/board-db/boards/FT_G6476

iopsys-brcm63xx-arm/base-files/etc/board-db/boards/FT_P3410B

iopsys-brcm63xx-arm/base-files/etc/board-db/boards/FT_P3414B

iopsys-brcm63xx-arm/base-files/etc/board-db/boards/FT_P6414

iopsys-brcm63xx-arm/base-files/etc/board-db/boards/FT_P6426