layers: Remove redundant device ext dep checks
layers: Remove redundant device ext dep checks

These are now handled through code-gen.

Change-Id: I1430f25fbe151b5581bb57292e733e8ba66cbdf7

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