opencl: add ABS op

[Gezahegne]

Overview

Adds support for the ABS unary operation (y = |x|) to the OpenCL backend.
This implements it for F32 and F16, contiguous and non-contiguous tensors.
The implementation mirrors the existing EXPM1 op (same element-wise unary
structure); only the per-element math differs (exp(x) - 1 → fabs(x)).

Additional information

Changes

• ggml/src/ggml-opencl/kernels/abs.cl (new): 6 kernels —
  kernel_abs_f32, kernel_abs_f32_4, kernel_abs_f32_nc,
  kernel_abs_f16, kernel_abs_f16_4, kernel_abs_f16_nc.
• ggml/src/ggml-opencl/CMakeLists.txt: register abs in GGML_OPENCL_KERNELS.
• ggml/src/ggml-opencl/ggml-opencl.cpp:
  • declare the 6 cl_kernel kernel_abs_* handles in the backend context,
  • load them in a new // abs program block,
  • add the ggml_cl_abs() dispatch function (contiguous fast path with _4
    vectorization when nelements % 4 == 0, otherwise scalar; _nc for
    non-contiguous inputs),
  • route GGML_UNARY_OP_ABS to ggml_cl_abs,
  • return true for GGML_UNARY_OP_ABS (F32/F16) in supports_op.
• docs/ops.md: regenerated — OpenCL ABS cell flips ❌ → ✅.

Requirements

• I have read and agree with the contributing guidelines
• AI usage disclosure:
  YES — used Claude Code to help implement the ABS OpenCL kernels and dispatch by mirroring the existing EXPM1 op, and regenerate docs/ops.md. Reviewed and verified on Intel Arc 140V hardware.

[ggml-gh-bot]

Hi @Gezahegne, thanks for your contribution!

Per our contribution guidelines, the automated PR checker found the following issue(s) that need your attention:

• AI-generated content: This project does not accept PRs, descriptions or commit messages that are fully or predominantly AI-generated. If you have used AI to assist you in writing code, please make sure to disclose that explicitly.

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Please note that maintainers reserve the right to make final decisions on PRs. If you believe there is a mistake, please comment below.

[arthw]

Could you remove the string "SYCL" in the description?
We use it as key word to filter the PR/issue for different backends.

Thank you!

[max-krasnyansky]

Please remove changes in .gitignore and extra txt files.
Also looks like you need to rebase with latest master.