Fix pytorch 2.0 cross attention not working.

comfy/ldm/modules/attention.py

@@ -489,6 +489,8 @@ if XFORMERS_IS_AVAILBLE == False or "--disable-xformers" in sys.argv:
         if "--use-pytorch-cross-attention" in sys.argv:
             print("Using pytorch cross attention")
             torch.backends.cuda.enable_math_sdp(False)
+            torch.backends.cuda.enable_flash_sdp(True)
+            torch.backends.cuda.enable_mem_efficient_sdp(True)
             CrossAttention = CrossAttentionPytorch
         else:
             print("Using sub quadratic optimization for cross attention, if you have memory or speed issues try using: --use-split-cross-attention")
@@ -497,6 +499,7 @@ else:
     print("Using xformers cross attention")
     CrossAttention = MemoryEfficientCrossAttention
 
+
 class BasicTransformerBlock(nn.Module):
     def __init__(self, dim, n_heads, d_head, dropout=0., context_dim=None, gated_ff=True, checkpoint=True,
                  disable_self_attn=False):