hwrng: add devm_* interfaces

This change adds devm_hwrng_register and devm_hwrng_unregister which
use can simplify error unwinding and unbinding code paths in device
drivers.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h
index eb7b414..4f7d8f4 100644
--- a/include/linux/hw_random.h
+++ b/include/linux/hw_random.h
@@ -50,10 +50,14 @@
 	struct completion cleanup_done;
 };
 
+struct device;
+
 /** Register a new Hardware Random Number Generator driver. */
 extern int hwrng_register(struct hwrng *rng);
+extern int devm_hwrng_register(struct device *dev, struct hwrng *rng);
 /** Unregister a Hardware Random Number Generator driver. */
 extern void hwrng_unregister(struct hwrng *rng);
+extern void devm_hwrng_unregister(struct device *dve, struct hwrng *rng);
 /** Feed random bits into the pool. */
 extern void add_hwgenerator_randomness(const char *buffer, size_t count, size_t entropy);