Fix copy-paste error in phi4mm image processing

[lifuhuang]

The current Phi4mm implementation only supports pixels as input but not embeddings.

The existing embedding handling logic code seems to mistakenly copied from other models -- it's referring to modules not existing in phi4mm self.visual (in phi4mm, the encoding module is vision_encoder)

if image_input["type"] == "image_embeds":
            image_embeds = image_input["image_embeds"].type(self.visual.dtype)

[github-actions]

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