Allow k pipeline to generate > 1 images (huggingface#1645)

Allow k pipeline to generate > 1 images.

Author: pcuenca

src/diffusers/pipelines/stable_diffusion/pipeline_stable_diffusion_k_diffusion.py

@@ -439,6 +439,7 @@ def __call__(
         # 6. Define model function
         def model_fn(x, t):
             latent_model_input = torch.cat([x] * 2)
+            t = torch.cat([t] * 2)
 
             noise_pred = self.k_diffusion_model(latent_model_input, t, cond=text_embeddings)