Fix spelling errors present in UI files

plugins/samplesource/hackrfinput/hackrfinputgui.ui

@@ -193,7 +193,7 @@
      <item row="0" column="1">
       <widget class="QSlider" name="LOppm">
        <property name="toolTip">
-        <string>Local Oscullator ppm correction</string>
+        <string>Local Oscillator ppm correction</string>
        </property>
        <property name="minimum">
         <number>-300</number>
@@ -461,7 +461,7 @@
      <item row="0" column="4">
       <widget class="QComboBox" name="bbFilter">
        <property name="toolTip">
-        <string>RF bandpas filter</string>
+        <string>RF bandpass filter</string>
        </property>
       </widget>
      </item>

plugins/samplesource/rtlsdr/rtlsdrgui.ui

@@ -260,7 +260,7 @@
         </size>
        </property>
        <property name="toolTip">
-        <string>Relative postion of device center frequency</string>
+        <string>Relative position of device center frequency</string>
        </property>
        <property name="currentIndex">
         <number>2</number>

plugins/samplesource/sdrdaemonsource/sdrdaemonsourcegui.ui

@@ -527,7 +527,7 @@
         </size>
        </property>
        <property name="toolTip">
-        <string>Number of uncrecoverable errors since event counts reset</string>
+        <string>Number of unrecoverable errors since event counts reset</string>
        </property>
        <property name="text">
         <string>000</string>

plugins/samplesource/testsource/testsourcegui.ui

@@ -287,7 +287,7 @@
         </size>
        </property>
        <property name="toolTip">
-        <string>Relative postion of generator center frequency</string>
+        <string>Relative position of generator center frequency</string>
        </property>
        <property name="currentIndex">
         <number>2</number>