DataFlash: AT45DB021 fix and AT45DB081 support

Fix for page size of AT45DB021. Also adding bigger AT45DB081
which comes with some newer boards.

Signed-off-by: Sergey Lapin <slapin@ossfans.org>
diff --git a/include/dataflash.h b/include/dataflash.h
index 80f0633..de04139 100644
--- a/include/dataflash.h
+++ b/include/dataflash.h
@@ -135,9 +135,9 @@
 	int cs;
 };
 /*-------------------------------------------------------------------------------------------------*/
-
 #define AT45DB161	0x2c
 #define AT45DB021	0x14
+#define AT45DB081	0x24
 #define AT45DB321	0x34
 #define AT45DB642	0x3c
 #define AT45DB128	0x10