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/ethernut5_defconfig b/configs/ethernut5_defconfig
index 01d0098..1b083ca 100644
--- a/configs/ethernut5_defconfig
+++ b/configs/ethernut5_defconfig
@@ -10,6 +10,7 @@
 CONFIG_ENV_SECT_SIZE=0x21000
 CONFIG_DM_GPIO=y
 CONFIG_DEFAULT_DEVICE_TREE="ethernut5"
+CONFIG_SYS_LOAD_ADDR=0x020000000
 CONFIG_SYS_EXTRA_OPTIONS="AT91SAM9XE"
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y