vo/vulkan/context_display: init fd to -1

Instead of using zero initialized value. Otherwise an early init failure
calls close(0), a descriptor we don't own, breaking whatever else
happens to hold it.

This is bit defensive, but I want to init those just after allocation,
so we don't have to trace whether they are initalized correctly or not.

video/out/vulkan/context_display.c

@@ -377,6 +377,10 @@ static bool display_init(struct ra_ctx *ctx)
 
     VkDisplayModePropertiesKHR *mode = NULL;
 
+#if HAVE_DRM
+    p->drm_params.fd = -1;
+    p->drm_params.render_fd = -1;
+#endif
     p->opts = mp_get_config_group(p, ctx->global, &vulkan_display_conf);
     int display_idx = p->opts->display;
     int mode_idx = p->opts->mode;