Skip temporary variable for SHA1DC_ALLOW_UNALIGNED_ACCESS

This is the feedback I left on pull request #30[1] turned into a
patch.

1. https://github.com/cr-marcstevens/sha1collisiondetection/pull/30
diff --git a/lib/sha1.c b/lib/sha1.c
index 587158c..3dff80a 100644
--- a/lib/sha1.c
+++ b/lib/sha1.c
@@ -1748,7 +1748,6 @@
 void SHA1DCUpdate(SHA1_CTX* ctx, const char* buf, size_t len)
 {
 	unsigned left, fill;
-	const uint32_t* buffer_to_hash = NULL;
 
 	if (len == 0)
 		return;
@@ -1770,12 +1769,11 @@
 		ctx->total += 64;
 
 #if defined(SHA1DC_ALLOW_UNALIGNED_ACCESS)
-		buffer_to_hash = (const uint32_t*)buf;
+		sha1_process(ctx, (uint32_t*)(buf));
 #else
-		buffer_to_hash = (const uint32_t*)ctx->buffer;
 		memcpy(ctx->buffer, buf, 64);
+		sha1_process(ctx, (uint32_t*)(ctx->buffer));
 #endif /* defined(SHA1DC_ALLOW_UNALIGNED_ACCESS) */
-		sha1_process(ctx, buffer_to_hash);
 		buf += 64;
 		len -= 64;
 	}