Use single sha256 for txid

bitcoin/shadouble.c

@@ -11,12 +11,22 @@ void sha256_double(struct sha256_double *shadouble, const void *p, size_t len)
 	sha256(&shadouble->sha, &shadouble->sha, sizeof(shadouble->sha));
 }
 
+void sha256_single(struct sha256_double *shasingle, const void *p, size_t len)
+{
+	sha256(&shasingle->sha, memcheck(p, len), len);
+}
+
 void sha256_double_done(struct sha256_ctx *shactx, struct sha256_double *res)
 {
 	sha256_done(shactx, &res->sha);
 	sha256(&res->sha, &res->sha, sizeof(res->sha));
 }
 
+void sha256_single_done(struct sha256_ctx *shactx, struct sha256_double *res)
+{
+	sha256_done(shactx, &res->sha);
+}
+
 REGISTER_TYPE_TO_HEXSTR(sha256_double);
 
 void towire_sha256_double(u8 **pptr, const struct sha256_double *sha256d)

bitcoin/shadouble.h

@@ -13,6 +13,10 @@ void sha256_double(struct sha256_double *shadouble, const void *p, size_t len);
 
 void sha256_double_done(struct sha256_ctx *sha256, struct sha256_double *res);
 
+void sha256_single(struct sha256_double *shasingle, const void *p, size_t len);
+
+void sha256_single_done(struct sha256_ctx *sha256, struct sha256_double *res);
+
 /* marshal/unmarshal functions */
 void fromwire_sha256_double(const u8 **cursor, size_t *max,
 			    struct sha256_double *sha256d);

bitcoin/tx.c

@@ -482,7 +482,7 @@ void wally_txid(const struct wally_tx *wtx, struct bitcoin_txid *txid)
 	res = wally_tx_to_bytes(wtx, 0, arr, len, &written);
 	assert(len == written);
 
-	sha256_double(&txid->shad, arr, len);
+	sha256_single(&txid->shad, arr, len);
 	tal_free(arr);
 }