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/arch/arm/mach-at91/armv7/clock.c b/arch/arm/mach-at91/armv7/clock.c
index 3640fce..3926896 100644
--- a/arch/arm/mach-at91/armv7/clock.c
+++ b/arch/arm/mach-at91/armv7/clock.c
@@ -10,6 +10,7 @@
  */
 
 #include <common.h>
+#include <linux/delay.h>
 #include <linux/errno.h>
 #include <asm/io.h>
 #include <asm/arch/hardware.h>