common: Drop flash.h from common header

Move this uncommon header out of the common header.

Fix up some style problems in flash.h while we are here.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/dfu/dfu_sf.c

@@ -4,6 +4,7 @@
  */
 
 #include <common.h>
+#include <flash.h>
 #include <malloc.h>
 #include <errno.h>
 #include <div64.h>