flash: add Stellaris Blizzard class

Change-Id: I83f0d6edf3ab31d9fa86682f20cec77dc47ba2f6
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/146
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>

src/flash/nor/stellaris.c

@@ -377,7 +377,7 @@ static char * StellarisClassname[7] =
 	"Unknown",
 	"DustDevil",
 	"Tempest",
-	"Unknown",
+	"Blizzard",
 	"Firestorm"
 };