Model CPU offload fix for BLIPDiffusion

[DN6]

What does this PR do?

Currently enable_model_cpu_offload does not work for BLIPDiffusion.

This PR:

1. Adds the mode_cpu_offload_seq string to the BLIPDIffusionPipeline and BLIPDiffusionControlnetPipeline
2. Makes some changes to the device used in the pipeline call to avoid device mismatch errors.

Fixes # (issue)

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[patrickvonplaten]

Thanks

[sayakpaul]

The sequence string specifier is really sick!