Add 100ms more time to end of k4_set_ptt.

Had one report of K4 infrequently not returning to RX from TX when in Fake It mode.
Suspect a little more time is needed between TQ0; response and FA freq set

rigs/kenwood/k3.c

@@ -488,7 +488,7 @@ const struct rig_caps k4_caps =
     RIG_MODEL(RIG_MODEL_K4),
     .model_name =       "K4",
     .mfg_name =     "Elecraft",
-    .version =      BACKEND_VER ".21",
+    .version =      BACKEND_VER ".22",
     .copyright =        "LGPL",
     .status =       RIG_STATUS_STABLE,
     .rig_type =     RIG_TYPE_TRANSCEIVER,
@@ -2751,8 +2751,9 @@ int k4_set_ptt(RIG *rig, vfo_t vfo, ptt_t ptt)
             hl_usleep(100 * 1000);
             rig_debug(RIG_DEBUG_TRACE, "%s: ptt=%d, expected=%d\n", __func__, ptt2, ptt);
         }
-
     }
+    // had one report of Fake It not returning to RX freq after TX -- so a little more time for the K4
+    hl_usleep(100 * 1000);
 
     return RIG_OK;
 }