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/netspace_mini_v2_defconfig b/configs/netspace_mini_v2_defconfig
index bafc057..08fed94 100644
--- a/configs/netspace_mini_v2_defconfig
+++ b/configs/netspace_mini_v2_defconfig
@@ -11,6 +11,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="kirkwood-ns2mini"
 CONFIG_IDENT_STRING=" NS v2 Mini"
 # CONFIG_SYS_MALLOC_F is not set
+CONFIG_SYS_LOAD_ADDR=0x800000
 CONFIG_SYS_EXTRA_OPTIONS="NETSPACE_MINI_V2"
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y