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/cubieboard7_defconfig b/configs/cubieboard7_defconfig
index 8efb94d..da5806e 100644
--- a/configs/cubieboard7_defconfig
+++ b/configs/cubieboard7_defconfig
@@ -4,6 +4,7 @@
 CONFIG_MACH_S700=y
 CONFIG_IDENT_STRING="\ncubieboard7"
 CONFIG_DISTRO_DEFAULTS=y
+CONFIG_SYS_LOAD_ADDR=0x7ffc0
 CONFIG_BOOTDELAY=5
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyOWL3,115200n8"