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/imx8mm_data_modul_edm_sbc_defconfig b/configs/imx8mm_data_modul_edm_sbc_defconfig
index 3e141ae..fbc6cec 100644
--- a/configs/imx8mm_data_modul_edm_sbc_defconfig
+++ b/configs/imx8mm_data_modul_edm_sbc_defconfig
@@ -42,6 +42,8 @@
 CONFIG_ARCH_MISC_INIT=y
 CONFIG_BOARD_LATE_INIT=y
 CONFIG_SPL_MAX_SIZE=0x25000
+CONFIG_SPL_HAS_BSS_LINKER_SECTION=y
+CONFIG_SPL_BSS_START_ADDR=0x910000
 CONFIG_SPL_BSS_MAX_SIZE=0x2000
 # CONFIG_SPL_RAW_IMAGE_SUPPORT is not set
 CONFIG_SPL_LEGACY_IMAGE_FORMAT=y