uboot: forcefully update ethaddr environment

Added an update path that allows boards to reload their ethaddr
environment. This allows boards to automatically pickup the address when
its been burned into EEPROM. (This enables v2.4 to potentially also get
updated with new OUI assigned adresses)

tp2bmc/configs/tp2bmc_defconfig

@@ -44,7 +44,7 @@ BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
 BR2_TARGET_UBOOT_CUSTOM_GIT=y
 BR2_TARGET_UBOOT_CUSTOM_REPO_URL="https://github.com/turing-machines/u-boot.git"
-BR2_TARGET_UBOOT_CUSTOM_REPO_VERSION="b2ae364c5f774bd164a8ec4a4afc6488806e0bff"
+BR2_TARGET_UBOOT_CUSTOM_REPO_VERSION="540468d5d61505b1f21e1fb753c55b81ea634b00"
 BR2_TARGET_UBOOT_USE_CUSTOM_CONFIG=y
 BR2_TARGET_UBOOT_CUSTOM_CONFIG_FILE="$(BR2_EXTERNAL_TP2BMC_PATH)/board/tp2bmc/uboot_defconfig"
 BR2_TARGET_UBOOT_NEEDS_DTC=y