Qt4: Video Effects: Force puzzle to be in [2:16]x[2:16] range

If you go under 2x2, it can go seriously bersek.
(cherry picked from commit cdfe9a89)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/qt4/ui/video_effects.ui

@@ -488,7 +488,10 @@
        <item row="0" column="1" >
         <widget class="QSpinBox" name="puzzleRowsSpin" >
          <property name="minimum" >
-          <number>1</number>
+          <number>2</number>
+         </property>
+         <property name="maximum" >
+          <number>16</number>
          </property>
          <property name="value" >
           <number>3</number>
@@ -498,7 +501,10 @@
        <item row="1" column="1" >
         <widget class="QSpinBox" name="puzzleColsSpin" >
          <property name="minimum" >
-          <number>1</number>
+          <number>2</number>
+         </property>
+         <property name="maximum" >
+          <number>16</number>
          </property>
          <property name="value" >
           <number>3</number>