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/da850evm_nand_defconfig b/configs/da850evm_nand_defconfig
index 7803bf5..241f8ce 100644
--- a/configs/da850evm_nand_defconfig
+++ b/configs/da850evm_nand_defconfig
@@ -17,6 +17,7 @@
 CONFIG_SPL_SPI_FLASH_SUPPORT=y
 CONFIG_SPL_SPI_SUPPORT=y
 CONFIG_LTO=y
+CONFIG_SYS_LOAD_ADDR=0xc0700000
 CONFIG_SYS_EXTRA_OPTIONS="MAC_ADDR_IN_SPIFLASH"
 CONFIG_BOOTDELAY=3
 CONFIG_DEFAULT_FDT_FILE="da850-evm.dtb"