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/espresso7420_defconfig b/configs/espresso7420_defconfig
index a079acc..55671ab 100644
--- a/configs/espresso7420_defconfig
+++ b/configs/espresso7420_defconfig
@@ -8,6 +8,7 @@
 CONFIG_ENV_SIZE=0x4000
 CONFIG_DEFAULT_DEVICE_TREE="exynos7420-espresso7420"
 CONFIG_IDENT_STRING=" for ESPRESSO7420"
+CONFIG_SYS_LOAD_ADDR=0x43e00000
 # CONFIG_AUTOBOOT is not set
 CONFIG_SILENT_CONSOLE=y
 CONFIG_CONSOLE_MUX=y