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/board/renesas/sh7752evb/sh7752evb.c b/board/renesas/sh7752evb/sh7752evb.c
index 203eecf..135aaa5 100644
--- a/board/renesas/sh7752evb/sh7752evb.c
+++ b/board/renesas/sh7752evb/sh7752evb.c
@@ -5,6 +5,7 @@
 
 #include <common.h>
 #include <env.h>
+#include <flash.h>
 #include <init.h>
 #include <malloc.h>
 #include <asm/processor.h>