vo/opengl/context_drm_egl: 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/opengl/context_drm_egl.c

@@ -562,6 +562,8 @@ static bool drm_egl_init(struct ra_ctx *ctx)
         goto err;
 
     struct priv *p = ctx->priv = talloc_zero(ctx, struct priv);
+    p->drm_params.fd = -1;
+    p->drm_params.render_fd = -1;
     struct vo_drm_state *drm = ctx->vo->drm;
 
     if (ctx->vo->drm->opts->draw_surface_size.wh_valid) {