Allow 2nd rotator port for RT-21 Az/El model

https://github.com/Hamlib/Hamlib/issues/747

rotators/rotorez/rotorez.c

@@ -90,6 +90,7 @@ struct rotorez_rot_priv_data
  */
 
 static int rotorez_send_priv_cmd(ROT *rot, const char *cmd);
+static int rotorez_send_priv_cmd2(ROT *rot, const char *cmd);
 static int rotorez_flush_buffer(ROT *rot);
 
 /*
@@ -309,7 +310,7 @@ const struct rot_caps rt21_rot_caps =
     ROT_MODEL(ROT_MODEL_RT21),
     .model_name =       "RT-21",
     .mfg_name =     "Green Heron",
-    .version =      "20210723.0",
+    .version =      "20210801.0",
     .copyright =        "LGPL",
     .status =       RIG_STATUS_STABLE,
     .rot_type =     ROT_TYPE_OTHER,
@@ -488,6 +489,15 @@ static int rt21_rot_set_position(ROT *rot, azimuth_t azimuth,
         return err;
     }
 
+    if (rot->state.rotport2.pathname[0] != 0)
+    sprintf(cmdstr, "AP1%05.1f\r;", elevation);   /* Total field width of 5 chars */
+    err = rotorez_send_priv_cmd2(rot, cmdstr);
+
+    if (err != RIG_OK)
+    {
+        return err;
+    }
+
     return RIG_OK;
 }
 
@@ -1003,6 +1013,30 @@ static int rotorez_send_priv_cmd(ROT *rot, const char *cmdstr)
     return RIG_OK;
 }
 
+// send command to 2nd rotator port
+static int rotorez_send_priv_cmd2(ROT *rot, const char *cmdstr)
+{
+    struct rot_state *rs;
+    int err;
+
+    rig_debug(RIG_DEBUG_VERBOSE, "%s called\n", __func__);
+
+    if (!rot)
+    {
+        return -RIG_EINVAL;
+    }
+
+    rs = &rot->state;
+    err = write_block(&rs->rotport2, cmdstr, strlen(cmdstr));
+
+    if (err != RIG_OK)
+    {
+        return err;
+    }
+
+    return RIG_OK;
+}
+
 
 /*
  * Flush the serial input buffer