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/ls1046ardb_emmc_defconfig b/configs/ls1046ardb_emmc_defconfig
index 11725e5..7b42e8d 100644
--- a/configs/ls1046ardb_emmc_defconfig
+++ b/configs/ls1046ardb_emmc_defconfig
@@ -40,6 +40,8 @@
 CONFIG_MISC_INIT_R=y
 CONFIG_SPL_MAX_SIZE=0x1f000
 CONFIG_SPL_PAD_TO=0x21000
+CONFIG_SPL_HAS_BSS_LINKER_SECTION=y
+CONFIG_SPL_BSS_START_ADDR=0x8f000000
 CONFIG_SPL_BSS_MAX_SIZE=0x80000
 CONFIG_SPL_FSL_PBL=y
 CONFIG_SPL_BOARD_INIT=y