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/thunderx_88xx_defconfig b/configs/thunderx_88xx_defconfig
index 97a41d8..af4572d 100644
--- a/configs/thunderx_88xx_defconfig
+++ b/configs/thunderx_88xx_defconfig
@@ -8,6 +8,7 @@
 CONFIG_DEBUG_UART_CLOCK=24000000
 CONFIG_IDENT_STRING=" for Cavium Thunder CN88XX ARM v8 Multi-Core"
 CONFIG_DEBUG_UART=y
+CONFIG_SYS_LOAD_ADDR=0x500000
 CONFIG_BOOTDELAY=5
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyAMA0,115200n8 earlycon=pl011,0x87e024000000 debug maxcpus=48 rootwait rw root=/dev/sda2 coherent_pool=16M"