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/j721s2_evm_r5_defconfig b/configs/j721s2_evm_r5_defconfig
index c706ff3..1a548e7 100644
--- a/configs/j721s2_evm_r5_defconfig
+++ b/configs/j721s2_evm_r5_defconfig
@@ -35,6 +35,8 @@
 CONFIG_SPL_SIZE_LIMIT_SUBTRACT_GD=y
 CONFIG_SPL_SIZE_LIMIT_SUBTRACT_MALLOC=y
 CONFIG_SPL_MAX_SIZE=0xc0000
+CONFIG_SPL_HAS_BSS_LINKER_SECTION=y
+CONFIG_SPL_BSS_START_ADDR=0x41c76000
 CONFIG_SPL_BSS_MAX_SIZE=0xa000
 CONFIG_SPL_SYS_REPORT_STACK_F_USAGE=y
 CONFIG_SPL_BOARD_INIT=y