Blackfin: bf537-stamp: rename SPI/MMC define

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

include/configs/bf537-stamp.h

@@ -145,7 +145,7 @@
  * SPI_MMC Settings
  */
 #define CONFIG_MMC
-#define CONFIG_BFIN_SPI_MMC
+#define CONFIG_SPI_MMC
 
 
 /*