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/am65x_hs_evm_r5_defconfig b/configs/am65x_hs_evm_r5_defconfig
index 39ce527..d26f071 100644
--- a/configs/am65x_hs_evm_r5_defconfig
+++ b/configs/am65x_hs_evm_r5_defconfig
@@ -31,6 +31,8 @@
 CONFIG_USE_BOOTCOMMAND=y
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_SPL_MAX_SIZE=0x58000
+CONFIG_SPL_HAS_BSS_LINKER_SECTION=y
+CONFIG_SPL_BSS_START_ADDR=0x41c7effc
 CONFIG_SPL_BSS_MAX_SIZE=0xc00
 CONFIG_SPL_STACK_R=y
 CONFIG_SPL_SEPARATE_BSS=y