Convert CONFIG_SPL_BSS_START_ADDR to Kconfig

This converts the following to Kconfig:
   CONFIG_SPL_BSS_START_ADDR

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/draco_defconfig b/configs/draco_defconfig
index e5e1ba6..86c130f 100644
--- a/configs/draco_defconfig
+++ b/configs/draco_defconfig
@@ -36,6 +36,7 @@
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_ARCH_MISC_INIT=y
+CONFIG_SPL_BSS_START_ADDR=0x80000000
 CONFIG_SPL_I2C=y
 CONFIG_SPL_NAND_DRIVERS=y
 CONFIG_SPL_NAND_ECC=y