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/silinux_ek874_defconfig b/configs/silinux_ek874_defconfig
index 0377c9e..6a1b310 100644
--- a/configs/silinux_ek874_defconfig
+++ b/configs/silinux_ek874_defconfig
@@ -11,6 +11,7 @@
 CONFIG_SPL_TEXT_BASE=0xe6318000
 CONFIG_RCAR_GEN3=y
 CONFIG_TARGET_SILINUX_EK874=y
+CONFIG_SYS_LOAD_ADDR=0x58000000
 CONFIG_FIT=y
 CONFIG_SUPPORT_RAW_INITRD=y
 CONFIG_USE_BOOTARGS=y