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/tb100_defconfig b/configs/tb100_defconfig
index 99ef8a1..bedaa53 100644
--- a/configs/tb100_defconfig
+++ b/configs/tb100_defconfig
@@ -4,6 +4,7 @@
 CONFIG_ENV_SIZE=0x800
 CONFIG_DEFAULT_DEVICE_TREE="abilis_tb100"
 CONFIG_SYS_CLK_FREQ=500000000
+CONFIG_SYS_LOAD_ADDR=0x82000000
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200n8"