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/sama7g5ek_mmc1_defconfig b/configs/sama7g5ek_mmc1_defconfig
index e076e07..bd6cbcc 100644
--- a/configs/sama7g5ek_mmc1_defconfig
+++ b/configs/sama7g5ek_mmc1_defconfig
@@ -14,6 +14,7 @@
 CONFIG_DEBUG_UART_CLOCK=200000000
 CONFIG_DEBUG_UART=y
 CONFIG_ENV_VARS_UBOOT_CONFIG=y
+CONFIG_SYS_LOAD_ADDR=0x62000000
 CONFIG_FIT=y
 CONFIG_SD_BOOT=y
 CONFIG_USE_BOOTARGS=y