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/venice2_defconfig b/configs/venice2_defconfig
index cdc7606..3b60e13 100644
--- a/configs/venice2_defconfig
+++ b/configs/venice2_defconfig
@@ -8,6 +8,7 @@
 CONFIG_SPL_TEXT_BASE=0x80108000
 CONFIG_TEGRA124=y
 CONFIG_TARGET_VENICE2=y
+CONFIG_SYS_LOAD_ADDR=0x81000000
 CONFIG_OF_SYSTEM_SETUP=y
 CONFIG_CONSOLE_MUX=y
 CONFIG_SYS_STDIO_DEREGISTER=y