zink. Don't set incorrect sType in VkImportMemoryFdInfoKHR struct

imfi.sType was being set to an invalid value, triggering a warning in Clang. The only valid value for imfi.sType is VK_STRUCTURE_TYPE_IMPORT_MEMORY_FD_INFO_KHR which is the value it is being given at initialisation time, a few lines earlier. The incorrect value, VK_EXTERNAL_MEMORY_HANDLE_TYPE_OPAQUE_FD_BIT, is supposed to be used in imfi.handleType instead - and indeed, handleType is being set to this value a few lines later.