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/corvus_defconfig b/configs/corvus_defconfig
index 42c0a48..5d2c6a5 100644
--- a/configs/corvus_defconfig
+++ b/configs/corvus_defconfig
@@ -16,6 +16,7 @@
 CONFIG_SPL_SERIAL_SUPPORT=y
 CONFIG_SPL=y
 CONFIG_ENV_OFFSET_REDUND=0x180000
+CONFIG_SYS_LOAD_ADDR=0x70000000
 CONFIG_SYS_EXTRA_OPTIONS="AT91SAM9M10G45,MACH_TYPE=2066,SYS_USE_NANDFLASH"
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y