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>
diff --git a/common/flash.c b/common/flash.c
index 9601716..4a28ac5 100644
--- a/common/flash.c
+++ b/common/flash.c
@@ -8,6 +8,7 @@
 
 #include <common.h>
 #include <flash.h>
+#include <uuid.h>
 
 #include <mtd/cfi_flash.h>