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/nyan-big_defconfig b/configs/nyan-big_defconfig
index 3f6bb94..3e328d9 100644
--- a/configs/nyan-big_defconfig
+++ b/configs/nyan-big_defconfig
@@ -12,6 +12,7 @@
 CONFIG_TEGRA124=y
 CONFIG_TARGET_NYAN_BIG=y
 CONFIG_DEBUG_UART=y
+CONFIG_SYS_LOAD_ADDR=0x82408000
 CONFIG_FIT=y
 CONFIG_FIT_BEST_MATCH=y
 CONFIG_OF_SYSTEM_SETUP=y