[NFC][AMDGPU] don't test asyncmark for non-async variants on pre-gfx12 (#190774)
The test for asyncmark on pref-gfx12 targets, checks the effect of async
marks on both async and non-async instructions. This is achieved by a
sed invocation in the RUN line to remove the .async from intrinsic name.
Such a test serves no purpose other than a minor flex. The two sets of
CHECK lines using the WITH and WITHOUT prefix are not easy to compare by
a simple eyeballing. Eliminating this hack makes it easier to add GISEL
variants later. With and without GISEL, the combinations will increase
to four instead of the current two.
Assisted-By: Claude Opus 4.6