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/drivers/misc/cros_ec.c b/drivers/misc/cros_ec.c
index fa9984f..c145b67 100644
--- a/drivers/misc/cros_ec.c
+++ b/drivers/misc/cros_ec.c
@@ -18,6 +18,7 @@
 #include <common.h>
 #include <command.h>
 #include <dm.h>
+#include <flash.h>
 #include <i2c.h>
 #include <cros_ec.h>
 #include <fdtdec.h>