XTRX input: use NCO value as a delta from LO (like with LimeSDR)

plugins/samplesource/xtrxinput/xtrxinputgui.ui

@@ -6,7 +6,7 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>373</width>
+    <width>370</width>
     <height>290</height>
    </rect>
   </property>
@@ -240,23 +240,7 @@
       </widget>
      </item>
      <item>
-      <widget class="QPushButton" name="ncoReset">
-       <property name="maximumSize">
-        <size>
-         <width>22</width>
-         <height>22</height>
-        </size>
-       </property>
-       <property name="toolTip">
-        <string>Reset the NCO to zero frequency</string>
-       </property>
-       <property name="text">
-        <string>R</string>
-       </property>
-      </widget>
-     </item>
-     <item>
-      <widget class="ValueDial" name="ncoFrequency" native="true">
+      <widget class="ValueDialZ" name="ncoFrequency" native="true">
        <property name="sizePolicy">
         <sizepolicy hsizetype="Maximum" vsizetype="Maximum">
          <horstretch>0</horstretch>
@@ -1122,6 +1106,12 @@ QToolTip{background-color: white; color: black;}</string>
    <extends>QToolButton</extends>
    <header>gui/externalclockbutton.h</header>
   </customwidget>
+  <customwidget>
+   <class>ValueDialZ</class>
+   <extends>QWidget</extends>
+   <header>gui/valuedialz.h</header>
+   <container>1</container>
+  </customwidget>
  </customwidgets>
  <resources>
   <include location="../../../sdrgui/resources/res.qrc"/>