clk: add include guard to clk-conf.h

Add a header include guard just in case.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Link: https://lkml.kernel.org/r/20190820030536.1181-1-yamada.masahiro@socionext.comSigned-off-by: Stephen Boyd <sboyd@kernel.org>

include/linux/clk/clk-conf.h

@@ -4,6 +4,9 @@
  * Sylwester Nawrocki <s.nawrocki@samsung.com>
  */
 
+#ifndef __CLK_CONF_H
+#define __CLK_CONF_H
+
 #include <linux/types.h>
 
 struct device_node;
@@ -17,3 +20,5 @@ static inline int of_clk_set_defaults(struct device_node *node,
 	return 0;
 }
 #endif
+
+#endif /* __CLK_CONF_H */