ggml-hexagon: add PAD op HVX kernel (llama/23078)

* ggml-hexagon: add PAD op HVX kernel

Implements GGML_OP_PAD on the Hexagon HTP backend using HVX vectorized
kernels. Supports zero-padding and circular padding across all 4 tensor
dimensions.

* hex-ggml: remove duplicate op cases (merge conflict)

* hex-pad: fix editorconfig checks and macro alignment

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Co-authored-by: Max Krasnyansky <maxk@qti.qualcomm.com>