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/silinux_ek874_defconfig b/configs/silinux_ek874_defconfig
index ce211a9..24fcfae 100644
--- a/configs/silinux_ek874_defconfig
+++ b/configs/silinux_ek874_defconfig
@@ -24,6 +24,8 @@
 CONFIG_DEFAULT_FDT_FILE="r8a774c0-ek874.dtb"
 # CONFIG_BOARD_EARLY_INIT_F is not set
 CONFIG_SYS_MALLOC_BOOTPARAMS=y
+CONFIG_SPL_HAS_BSS_LINKER_SECTION=y
+CONFIG_SPL_BSS_START_ADDR=0xe631f000
 CONFIG_SPL_BSS_MAX_SIZE=0x1000
 # CONFIG_SPL_SHARES_INIT_SP_ADDR is not set
 CONFIG_SPL_STACK=0xe6304000