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/edison_defconfig b/configs/edison_defconfig
index a789630..56cb816 100644
--- a/configs/edison_defconfig
+++ b/configs/edison_defconfig
@@ -9,6 +9,7 @@
 CONFIG_TARGET_EDISON=y
 CONFIG_SMP=y
 CONFIG_GENERATE_ACPI_TABLE=y
+CONFIG_SYS_LOAD_ADDR=0x100000
 CONFIG_BOARD_EARLY_INIT_R=y
 CONFIG_LAST_STAGE_INIT=y
 CONFIG_HUSH_PARSER=y