[clang] [OpenMP] codegen support for masked combined construct parallel masked taskloop (PR #121741)

[CHANDRA GHALE via cfe-commits]

chandraghale wrote:

> Update OpenMPSupport.rst

Updated OpenMPSupport.rst . Updated the doc for all the related split-ed  PRs ( [PR-121746](https://github.com/llvm/llvm-project/pull/121746) , [121914](https://github.com/llvm/llvm-project/pull/121914) , [121916](https://github.com/llvm/llvm-project/pull/121916)  ) for combined masked construct in this PR only to avoid merge conflict. 

https://github.com/llvm/llvm-project/pull/121741