vk-layer-generate.py: handle device commands in GetInstanceProcAddr
vk-layer-generate.py: handle device commands in GetInstanceProcAddr

Per commit 5bf16c33b9c1f38fc467d94716f276620a265327, extension check is
bypassed in GetInstanceProcAddr for VK_KHR_swapchain functions.

Radamanthe/VulkanSamples,Radamanthe/VulkanSamples,Radamanthe/VulkanSamples,Radamanthe/VulkanSamples,Radamanthe/VulkanSamples,Radamanthe/VulkanSamples