utils: move BIT(n) macro to utils.h

We are duplicating this macro define, and it is useful enough
to be placed in the common place.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/plat/rockchip/rk3399/drivers/soc/soc.h b/plat/rockchip/rk3399/drivers/soc/soc.h
index 742bb7b..28590f2 100644
--- a/plat/rockchip/rk3399/drivers/soc/soc.h
+++ b/plat/rockchip/rk3399/drivers/soc/soc.h
@@ -31,6 +31,8 @@
 #ifndef __SOC_H__
 #define __SOC_H__
 
+#include <utils.h>
+
 #define GLB_SRST_FST_CFG_VAL	0xfdb9
 #define GLB_SRST_SND_CFG_VAL	0xeca8