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/durian_defconfig b/configs/durian_defconfig
index 77b9795..2388d87 100644
--- a/configs/durian_defconfig
+++ b/configs/durian_defconfig
@@ -8,6 +8,7 @@
 # CONFIG_PSCI_RESET is not set
 CONFIG_AHCI=y
 CONFIG_DISTRO_DEFAULTS=y
+CONFIG_SYS_LOAD_ADDR=0x90000000
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyAMA0,115200 earlycon=pl011,0x28001000 root=/dev/sda2 rw"
 # CONFIG_DISPLAY_CPUINFO is not set