Fix Cycles material slots list being too short

Bring it in line with Eevee.

Differential Revision: https://developer.blender.org/D11982

intern/cycles/blender/addon/ui.py

@@ -1102,7 +1102,7 @@ class CYCLES_PT_context_material(CyclesButtonsPanel, Panel):
 
         if ob:
             is_sortable = len(ob.material_slots) > 1
-            rows = 1
+            rows = 3
             if (is_sortable):
                 rows = 4