common: Drop linux/delay.h from common header

Move this uncommon header out of the common header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/examples/api/libgenwrap.c b/examples/api/libgenwrap.c
index 51d6273..3aa2228 100644
--- a/examples/api/libgenwrap.c
+++ b/examples/api/libgenwrap.c
@@ -12,6 +12,7 @@
 #include <common.h>
 #include <command.h>
 #include <hang.h>
+#include <linux/delay.h>
 #include <linux/types.h>
 #include <api_public.h>