crypto: rng - RNGs must return 0 in success case

Change the RNGs to always return 0 in success case.

This patch ensures that seqiv.c works with RNGs other than krng. seqiv
expects that any return code other than 0 is an error. Without the
patch, rfc4106(gcm(aes)) will not work when using a DRBG or an ANSI
X9.31 RNG.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/include/crypto/rng.h b/include/crypto/rng.h
index a16fb10..6e28ea5 100644
--- a/include/crypto/rng.h
+++ b/include/crypto/rng.h
@@ -103,8 +103,7 @@
  * This function fills the caller-allocated buffer with random numbers using the
  * random number generator referenced by the cipher handle.
  *
- * Return: > 0 function was successful and returns the number of generated
- *	   bytes; < 0 if an error occurred
+ * Return: 0 function was successful; < 0 if an error occurred
  */
 static inline int crypto_rng_get_bytes(struct crypto_rng *tfm,
 				       u8 *rdata, unsigned int dlen)