[clang] [llvm] [polly] [X86] Remove knl/knm specific ISAs supports (PR #92883)

[Freddy Ye via cfe-commits]

FreddyLeaf wrote:

gcc recently formally removed knl/knm supports at trunk: https://godbolt.org/z/nKvo1P48d
Per conclusion before in https://github.com/llvm/llvm-project/pull/75580, this patch removed specific ISA supports of knl/knm while keep -march/tune support

https://github.com/llvm/llvm-project/pull/92883