crypto: replace scatterwalk_sg_next with sg_next

Modify crypto drivers to use the generic SG helper since
both of them are equivalent and the one from crypto is redundant.

See also:
  468577abe37ff7b453a9ac613e0ea155349203ae   reverted in
  b2ab4a57b018aafbba35bff088218f5cc3d2142e

Signed-off-by: Cristian Stoica <cristian.stoica@freescale.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/crypto/ahash.c b/crypto/ahash.c
index dd28906..8acb88603 100644
--- a/crypto/ahash.c
+++ b/crypto/ahash.c
@@ -121,7 +121,7 @@
 	if (!walk->total)
 		return 0;
 
-	walk->sg = scatterwalk_sg_next(walk->sg);
+	walk->sg = sg_next(walk->sg);
 
 	return hash_walk_new_entry(walk);
 }