RTLSDR GUI: step 1 for mousewheel on ppm and decimation

plugins/samplesource/rtlsdr/rtlsdrgui.ui

@@ -234,6 +234,9 @@
        <property name="minimum">
         <number>-99</number>
        </property>
+       <property name="pageStep">
+        <number>1</number>
+       </property>
        <property name="orientation">
         <enum>Qt::Horizontal</enum>
        </property>
@@ -289,7 +292,7 @@
         <number>4</number>
        </property>
        <property name="pageStep">
-        <number>4</number>
+        <number>1</number>
        </property>
        <property name="value">
         <number>4</number>