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/stm32f769-disco_defconfig b/configs/stm32f769-disco_defconfig
index 40f94ac..70e7068 100644
--- a/configs/stm32f769-disco_defconfig
+++ b/configs/stm32f769-disco_defconfig
@@ -9,6 +9,7 @@
 CONFIG_STM32F7=y
 CONFIG_TARGET_STM32F746_DISCO=y
 CONFIG_DISTRO_DEFAULTS=y
+CONFIG_SYS_LOAD_ADDR=0x8008000
 CONFIG_BOOTDELAY=3
 CONFIG_AUTOBOOT_KEYED=y
 CONFIG_AUTOBOOT_PROMPT="Hit SPACE in %d seconds to stop autoboot.\n"