fdtdec: Support separate BSS for all XPL builds

Adjust the condition so that separate BSS can be deselected for TPL and
VPL.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/fdtdec.c b/lib/fdtdec.c
index 5edc8dd..106bb40 100644
--- a/lib/fdtdec.c
+++ b/lib/fdtdec.c
@@ -1232,7 +1232,7 @@
 
 #ifdef CONFIG_SPL_BUILD
 	/* FDT is at end of BSS unless it is in a different memory region */
-	if (IS_ENABLED(CONFIG_SPL_SEPARATE_BSS))
+	if (CONFIG_IS_ENABLED(SEPARATE_BSS))
 		fdt_blob = (ulong *)_image_binary_end;
 	else
 		fdt_blob = (ulong *)__bss_end;