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/rock-pi-n10-rk3399pro_defconfig b/configs/rock-pi-n10-rk3399pro_defconfig
index e5df677..041bb96 100644
--- a/configs/rock-pi-n10-rk3399pro_defconfig
+++ b/configs/rock-pi-n10-rk3399pro_defconfig
@@ -10,6 +10,7 @@
 CONFIG_DEBUG_UART_BASE=0xFF1A0000
 CONFIG_DEBUG_UART_CLOCK=24000000
 CONFIG_DEBUG_UART=y
+CONFIG_SYS_LOAD_ADDR=0x800800
 # CONFIG_ANDROID_BOOT_IMAGE is not set
 CONFIG_DEFAULT_FDT_FILE="rockchip/rk3399pro-rock-pi-n10.dtb"
 # CONFIG_CONSOLE_MUX is not set