[clang] [OpenCL] Add decls for cl_intel_subgroups_char, cl_intel_subgroups_long (PR #146655)

[Mészáros Gergely via cfe-commits]

Maetveis wrote:

> ⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

This file is not formatted currently, the changes should match the current formatting style.

https://github.com/llvm/llvm-project/pull/146655