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/aspenite_defconfig b/configs/aspenite_defconfig
index 37e6871..4eb0623 100644
--- a/configs/aspenite_defconfig
+++ b/configs/aspenite_defconfig
@@ -5,6 +5,7 @@
 CONFIG_NR_DRAM_BANKS=2
 CONFIG_ENV_SIZE=0x20000
 CONFIG_IDENT_STRING="\nMarvell-Aspenite DB"
+CONFIG_SYS_LOAD_ADDR=0x800000
 CONFIG_BOOTDELAY=3
 CONFIG_USE_PREBOOT=y
 # CONFIG_DISPLAY_BOARDINFO is not set