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/sifive_unmatched_defconfig b/configs/sifive_unmatched_defconfig
index 88b74a9..b13a0f8 100644
--- a/configs/sifive_unmatched_defconfig
+++ b/configs/sifive_unmatched_defconfig
@@ -12,6 +12,7 @@
 CONFIG_RISCV_SMODE=y
 # CONFIG_SPL_USE_ARCH_MEMMOVE is not set
 CONFIG_DISTRO_DEFAULTS=y
+CONFIG_SYS_LOAD_ADDR=0x80200000
 CONFIG_FIT=y
 CONFIG_SPL_LOAD_FIT_ADDRESS=0x84000000
 CONFIG_DEFAULT_FDT_FILE="sifive/hifive-unmatched-a00.dtb"