be like the kernel and only unroll if not small

src/lib/libc/hash/sha2.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: sha2.c,v 1.21 2014/12/19 14:30:44 deraadt Exp $	*/
+/*	$OpenBSD: sha2.c,v 1.22 2014/12/19 15:14:04 tedu Exp $	*/
 
 /*
  * FILE:	sha2.c
@@ -52,9 +52,11 @@
  *   #define SHA2_UNROLL_TRANSFORM
  *
  */
-#if defined(__amd64__)
+#ifndef SHA2_SMALL
+#if defined(__amd64__) || defined(__i386__)
 #define SHA2_UNROLL_TRANSFORM
 #endif
+#endif
 
 /*** SHA-224/256/384/512 Machine Architecture Definitions *****************/
 /*