layers: Remove redundant/unused param checker code
layers: Remove redundant/unused param checker code

Removes param checker sType and NULL check code that is now
 auto-generated.  Also remove empty functions and conditional
statements.

Change-Id: I8be8aab0bf3a8fa60219e1066a7d3d6c9d26ec05

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools