vk: Fix warning from missing initializer

Struct initializers need to be { 0, } to zero out the variable they're
initializing.

src/vulkan/meta.c

@@ -584,7 +584,7 @@ meta_emit_blit(struct anv_cmd_buffer *cmd_buffer,
       .sType = VK_STRUCTURE_TYPE_RENDER_PASS_CREATE_INFO,
       .renderArea = { { 0, 0 }, { dest->extent.width, dest->extent.height } },
       .colorAttachmentCount = 1,
-      .extent = { },
+      .extent = { 0, },
       .sampleCount = 1,
       .layers = 1,
       .pColorFormats = (VkFormat[]) { dest->format },