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/xilinx_zynqmp_mini_emmc1_defconfig b/configs/xilinx_zynqmp_mini_emmc1_defconfig
index 996e65d..56ece14 100644
--- a/configs/xilinx_zynqmp_mini_emmc1_defconfig
+++ b/configs/xilinx_zynqmp_mini_emmc1_defconfig
@@ -10,6 +10,7 @@
 CONFIG_SPL_SYS_MALLOC_F_LEN=0x600
 CONFIG_SPL=y
 # CONFIG_CMD_ZYNQMP is not set
+CONFIG_SYS_LOAD_ADDR=0x8000000
 CONFIG_FIT=y
 CONFIG_SUPPORT_RAW_INITRD=y
 # CONFIG_AUTOBOOT is not set