loader: Fix loader_unwrap_physical_device() to cast to correct type
loader: Fix loader_unwrap_physical_device() to cast to correct type

The trampoline loader_unwrap_physical_device() utility function was
casting the VkPhysicalDevice parameter to (loader_physical_device*)
instead of (loader_physical_device_tramp*). It worked previously because
it just so happened that the phys_dev member was in the same location in
both structs.

Change-Id: I3bee175df8b64b44ef2e440f7e43603ca0617da2

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