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/board/wandboard/spl.c b/board/wandboard/spl.c
index 816b9cb..04c351f 100644
--- a/board/wandboard/spl.c
+++ b/board/wandboard/spl.c
@@ -11,6 +11,7 @@
 #include <asm/arch/imx-regs.h>
 #include <asm/arch/iomux.h>
 #include <asm/arch/mx6-pins.h>
+#include <linux/delay.h>
 #include <linux/errno.h>
 #include <asm/gpio.h>
 #include <asm/mach-imx/iomux-v3.h>