hwrng: timeriomem - add include guard to timeriomem-rng.h

Add a header include guard just in case.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

include/linux/timeriomem-rng.h

@@ -5,6 +5,9 @@
  * Copyright (c) 2009 Alexander Clouter <alex@digriz.org.uk>
  */
 
+#ifndef _LINUX_TIMERIOMEM_RNG_H
+#define _LINUX_TIMERIOMEM_RNG_H
+
 struct timeriomem_rng_data {
 	void __iomem		*address;
 
@@ -14,3 +17,5 @@ struct timeriomem_rng_data {
 	/* bits of entropy per 1024 bits read */
 	unsigned int		quality;
 };
+
+#endif /* _LINUX_TIMERIOMEM_RNG_H */