Blackfin: tweak embedded LDR env config option

Use the common config option for extracting the environment for embedding
into LDR files and clarify the LDR-specific option.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/include/configs/cm-bf537u.h b/include/configs/cm-bf537u.h
index d1870a8..0ed5960 100644
--- a/include/configs/cm-bf537u.h
+++ b/include/configs/cm-bf537u.h
@@ -96,7 +96,7 @@
 #if (CONFIG_BFIN_BOOT_MODE == BFIN_BOOT_BYPASS)
 #define ENV_IS_EMBEDDED
 #else
-#define ENV_IS_EMBEDDED_CUSTOM
+#define CONFIG_ENV_IS_EMBEDDED_IN_LDR
 #endif
 #ifdef ENV_IS_EMBEDDED
 /* WARNING - the following is hand-optimized to fit within