crypto: don't pollute the global namespace with sg_next()

It's a subsystem function, prefix it as such.

Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/crypto/scatterwalk.c b/crypto/scatterwalk.c
index 3052f65..d6852c3 100644
--- a/crypto/scatterwalk.c
+++ b/crypto/scatterwalk.c
@@ -62,7 +62,7 @@
 		walk->offset += PAGE_SIZE - 1;
 		walk->offset &= PAGE_MASK;
 		if (walk->offset >= walk->sg->offset + walk->sg->length)
-			scatterwalk_start(walk, sg_next(walk->sg));
+			scatterwalk_start(walk, scatterwalk_sg_next(walk->sg));
 	}
 }