Convert CONFIG_STANDALONE_LOAD_ADDR to Kconfig

This converts the following to Kconfig:
   CONFIG_STANDALONE_LOAD_ADDR

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/sifive_unmatched_defconfig b/configs/sifive_unmatched_defconfig
index c390af2..3d96aa5 100644
--- a/configs/sifive_unmatched_defconfig
+++ b/configs/sifive_unmatched_defconfig
@@ -19,6 +19,7 @@
 CONFIG_DISTRO_DEFAULTS=y
 CONFIG_HAS_CUSTOM_SYS_INIT_SP_ADDR=y
 CONFIG_CUSTOM_SYS_INIT_SP_ADDR=0x80200000
+CONFIG_STANDALONE_LOAD_ADDR=0x80200000
 CONFIG_FIT=y
 CONFIG_SPL_LOAD_FIT_ADDRESS=0x84000000
 CONFIG_USE_PREBOOT=y