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/cmd/mem.c b/cmd/mem.c
index 423e6c1..4d88254 100644
--- a/cmd/mem.c
+++ b/cmd/mem.c
@@ -24,6 +24,7 @@
 #include <watchdog.h>
 #include <asm/io.h>
 #include <linux/compiler.h>
+#include <linux/delay.h>
 
 DECLARE_GLOBAL_DATA_PTR;