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/geekbox_defconfig b/configs/geekbox_defconfig
index 55892f0..78ee306 100644
--- a/configs/geekbox_defconfig
+++ b/configs/geekbox_defconfig
@@ -9,6 +9,7 @@
 CONFIG_DEBUG_UART_BASE=0xFF690000
 CONFIG_DEBUG_UART_CLOCK=24000000
 CONFIG_DEBUG_UART=y
+CONFIG_SYS_LOAD_ADDR=0x800800
 CONFIG_DEFAULT_FDT_FILE="rockchip/rk3368-geekbox.dtb"
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y