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/roc-pc-rk3399_defconfig b/configs/roc-pc-rk3399_defconfig
index 4e5c904..ec17e33 100644
--- a/configs/roc-pc-rk3399_defconfig
+++ b/configs/roc-pc-rk3399_defconfig
@@ -14,6 +14,7 @@
 CONFIG_SPL_SPI_FLASH_SUPPORT=y
 CONFIG_SPL_SPI_SUPPORT=y
 CONFIG_DEBUG_UART=y
+CONFIG_SYS_LOAD_ADDR=0x800800
 # CONFIG_ANDROID_BOOT_IMAGE is not set
 CONFIG_DEFAULT_FDT_FILE="rockchip/rk3399-roc-pc.dtb"
 CONFIG_DISPLAY_BOARDINFO_LATE=y