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/bf537-pnav.h b/include/configs/bf537-pnav.h
index 0f908ef..6627a04 100644
--- a/include/configs/bf537-pnav.h
+++ b/include/configs/bf537-pnav.h
@@ -94,7 +94,7 @@
  * Env Storage Settings
  */
 #if (CONFIG_BFIN_BOOT_MODE == BFIN_BOOT_SPI_MASTER)
-#define ENV_IS_EMBEDDED_CUSTOM
+#define CONFIG_ENV_IS_EMBEDDED_IN_LDR
 #define CONFIG_ENV_IS_IN_SPI_FLASH
 #define CONFIG_ENV_OFFSET	0x4000
 #else