Convert CONFIG_SYS_LOAD_ADDR to Kconfig

Now that we have consistent usage, migrate this symbol to Kconfig.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Rick Chen <rick@andestech.com>
diff --git a/configs/chromebit_mickey_defconfig b/configs/chromebit_mickey_defconfig
index acc3286..613da60 100644
--- a/configs/chromebit_mickey_defconfig
+++ b/configs/chromebit_mickey_defconfig
@@ -15,6 +15,7 @@
 CONFIG_SPL_SPI_SUPPORT=y
 CONFIG_SPL_PAYLOAD="u-boot.img"
 CONFIG_DEBUG_UART=y
+CONFIG_SYS_LOAD_ADDR=0x800800
 CONFIG_USE_PREBOOT=y
 CONFIG_DEFAULT_FDT_FILE="rk3288-veyron-mickey.dtb"
 # CONFIG_DISPLAY_CPUINFO is not set