For Icom rigs return bandwidth of 12000 for FM mode

https://github.com/Hamlib/Hamlib/issues/1066

rigs/icom/icom.c

@@ -2667,6 +2667,8 @@ int icom_get_mode(RIG *rig, vfo_t vfo, rmode_t *mode, pbwidth_t *width)
         }
     }
 
+    if (*mode == RIG_MODE_FM) *width = 12000;
+
     RETURNFUNC2(RIG_OK);
 }