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/blackstamp.h b/include/configs/blackstamp.h
index 9cbc17a..1e4c716 100644
--- a/include/configs/blackstamp.h
+++ b/include/configs/blackstamp.h
@@ -247,7 +247,7 @@
 #define CONFIG_BFIN_SPI
 /* For the M25P64 SCK Should be Kept < 20Mhz */
 #define CONFIG_ENV_SPI_MAX_HZ	20000000
-#define CONFIG_SF_DEFAULT_HZ	20000000
+#define CONFIG_SF_DEFAULT_SPEED	20000000
 #define CONFIG_SPI_FLASH
 #define CONFIG_SPI_FLASH_STMICRO