Blackfin: fix SPI flash speed define name

The SPI flash define is named CONFIG_SF_DEFAULT_SPEED, not
CONFIG_SF_DEFAULT_HZ, so fix the typos in the Blackfin boards.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/include/configs/bf537-srv1.h b/include/configs/bf537-srv1.h
index c1bff3e..727b7e7 100644
--- a/include/configs/bf537-srv1.h
+++ b/include/configs/bf537-srv1.h
@@ -104,7 +104,7 @@
  */
 #define CONFIG_BFIN_SPI
 #define CONFIG_ENV_SPI_MAX_HZ	30000000
-#define CONFIG_SF_DEFAULT_HZ	30000000
+#define CONFIG_SF_DEFAULT_SPEED	30000000
 #define CONFIG_SPI_FLASH
 #define CONFIG_SPI_FLASH_STMICRO