common: Drop linux/bitops.h from common header

Move this uncommon header out of the common header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/clk/at91/clk-system.c b/drivers/clk/at91/clk-system.c
index f9adef2..76b1958 100644
--- a/drivers/clk/at91/clk-system.c
+++ b/drivers/clk/at91/clk-system.c
@@ -7,6 +7,7 @@
 #include <common.h>
 #include <clk-uclass.h>
 #include <dm.h>
+#include <linux/bitops.h>
 #include <linux/io.h>
 #include <mach/at91_pmc.h>
 #include "pmc.h"