device_limits: intercept CmdSetScissor and CmdSetViepwort

They are defined but unused.
diff --git a/layers/device_limits.cpp b/layers/device_limits.cpp
index 74743e0..d5ad798 100644
--- a/layers/device_limits.cpp
+++ b/layers/device_limits.cpp
@@ -776,6 +776,8 @@
         { "vkCmdUpdateBuffer", reinterpret_cast<PFN_vkVoidFunction>(CmdUpdateBuffer) },
         { "vkUpdateDescriptorSets", reinterpret_cast<PFN_vkVoidFunction>(UpdateDescriptorSets) },
         { "vkCmdFillBuffer", reinterpret_cast<PFN_vkVoidFunction>(CmdFillBuffer) },
+        { "vkCmdSetScissor", reinterpret_cast<PFN_vkVoidFunction>(CmdSetScissor) },
+        { "vkCmdSetViewport", reinterpret_cast<PFN_vkVoidFunction>(CmdSetViewport) },
     };
 
     for (size_t i = 0; i < ARRAY_SIZE(core_device_commands); i++) {