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/firefly-px30_defconfig b/configs/firefly-px30_defconfig
index 64744d5..1d91cac 100644
--- a/configs/firefly-px30_defconfig
+++ b/configs/firefly-px30_defconfig
@@ -17,6 +17,7 @@
 CONFIG_DEBUG_UART_CLOCK=24000000
 CONFIG_DEBUG_UART=y
 CONFIG_TPL_SYS_MALLOC_F_LEN=0x600
+CONFIG_SYS_LOAD_ADDR=0x800800
 # CONFIG_ANDROID_BOOT_IMAGE is not set
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y