Fix bug in nistp224/256/521 where have_precompute_mult always returns 0

During precomputation if the group given is well known then we memcpy a
well known precomputation. However we go the wrong label in the code and
don't store the data properly. Consequently if we call have_precompute_mult
the data isn't there and we return 0.

RT#3600
Reviewed-by: NRichard Levitte <levitte@openssl.org>

crypto/ec/ecp_nistp224.c

@@ -1582,8 +1582,7 @@ int ec_GFp_nistp224_precompute_mult(EC_GROUP *group, BN_CTX *ctx)
      */
     if (0 == EC_POINT_cmp(group, generator, group->generator, ctx)) {
         memcpy(pre->g_pre_comp, gmul, sizeof(pre->g_pre_comp));
-        ret = 1;
-        goto err;
+        goto done;
     }
     if ((!BN_to_felem(pre->g_pre_comp[0][1][0], group->generator->X)) ||
         (!BN_to_felem(pre->g_pre_comp[0][1][1], group->generator->Y)) ||
@@ -1661,6 +1660,7 @@ int ec_GFp_nistp224_precompute_mult(EC_GROUP *group, BN_CTX *ctx)
     }
     make_points_affine(31, &(pre->g_pre_comp[0][1]), tmp_felems);
 
+ done:
     SETPRECOMP(group, nistp224, pre);
     pre = NULL;
     ret = 1;

crypto/ec/ecp_nistp256.c

@@ -2207,8 +2207,7 @@ int ec_GFp_nistp256_precompute_mult(EC_GROUP *group, BN_CTX *ctx)
      */
     if (0 == EC_POINT_cmp(group, generator, group->generator, ctx)) {
         memcpy(pre->g_pre_comp, gmul, sizeof(pre->g_pre_comp));
-        ret = 1;
-        goto err;
+        goto done;
     }
     if ((!BN_to_felem(x_tmp, group->generator->X)) ||
         (!BN_to_felem(y_tmp, group->generator->Y)) ||
@@ -2295,6 +2294,7 @@ int ec_GFp_nistp256_precompute_mult(EC_GROUP *group, BN_CTX *ctx)
     }
     make_points_affine(31, &(pre->g_pre_comp[0][1]), tmp_smallfelems);
 
+ done:
     SETPRECOMP(group, nistp256, pre);
     pre = NULL;
     ret = 1;

crypto/ec/ecp_nistp521.c

@@ -2031,8 +2031,7 @@ int ec_GFp_nistp521_precompute_mult(EC_GROUP *group, BN_CTX *ctx)
      */
     if (0 == EC_POINT_cmp(group, generator, group->generator, ctx)) {
         memcpy(pre->g_pre_comp, gmul, sizeof(pre->g_pre_comp));
-        ret = 1;
-        goto err;
+        goto done;
     }
     if ((!BN_to_felem(pre->g_pre_comp[1][0], group->generator->X)) ||
         (!BN_to_felem(pre->g_pre_comp[1][1], group->generator->Y)) ||
@@ -2090,6 +2089,7 @@ int ec_GFp_nistp521_precompute_mult(EC_GROUP *group, BN_CTX *ctx)
     }
     make_points_affine(15, &(pre->g_pre_comp[1]), tmp_felems);
 
+ done:
     SETPRECOMP(group, nistp521, pre);
     ret = 1;
     pre = NULL;