For kenwood rigs reset split after set_vfo FR command if needed

Side effect of this change is support of reverse split by changing to VFOB
https://github.com/Hamlib/Hamlib/issues/746

rigs/kenwood/kenwood.c

@@ -1118,6 +1118,20 @@ int kenwood_set_vfo(RIG *rig, vfo_t vfo)
 
     snprintf(cmdbuf, sizeof(cmdbuf), "FR%c", vfo_function);
 
+    // as we change VFO we will change split to the other VFO
+    // some rigs turn split off with FR command 
+    if (priv->split)
+    {
+        if (vfo_function == '0')
+        {
+            strcat(cmdbuf, ";FT1");
+        }
+        else
+        {
+            strcat(cmdbuf, ";FT0");
+        }
+    }
+
     if (RIG_IS_TS50 || RIG_IS_TS940)
     {
         cmdbuf[1] = 'N';

rigs/kenwood/kenwood.h

@@ -28,7 +28,7 @@
 #include "token.h"
 #include "misc.h"
 
-#define BACKEND_VER "20210827"
+#define BACKEND_VER "20210828"
 
 #define EOM_KEN ';'
 #define EOM_TH '\r'