[llvm] [offload] Use pinned memory for KLE (PR #213767)

[Robert Imschweiler via llvm-commits]

ro-i wrote:

In pushMemoryCopyH2DAsync, the host-to-host copy might be issued as an hsa async handler and it's gated by InputSignal, while with this patch, it's a plain, ungated host memcpy.

https://github.com/llvm/llvm-project/pull/213767