test: Load mac address with i2c eeprom

This uses an i2c eeprom to load a mac address using the nvmem interface.
Enable I2C_EEPROM for sandbox SPL since it is the only sandbox config
which doesn't enable it eeprom.

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/sandbox_spl_defconfig b/configs/sandbox_spl_defconfig
index b45f478..ec2d26d 100644
--- a/configs/sandbox_spl_defconfig
+++ b/configs/sandbox_spl_defconfig
@@ -155,6 +155,7 @@
 CONFIG_P2SB=y
 CONFIG_PWRSEQ=y
 CONFIG_SPL_PWRSEQ=y
+CONFIG_I2C_EEPROM=y
 CONFIG_MMC_SANDBOX=y
 CONFIG_SPI_FLASH_SANDBOX=y
 CONFIG_SPI_FLASH_ATMEL=y