[llvm] [AMDGPU] Fix and enable NONGFX90A check prefix (PR #96152)

[Matt Arsenault via llvm-commits]

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@@ -86,7 +86,6 @@
 .end_amdhsa_kernel
 
 // ALL-LABEL: warning: test_amdhsa_accum_offset_missing
-// NONGFX9A: error: directive requires gfx90a+
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arsenm wrote:

Usually these are we missed a check for error somewhere earlier in the file. Really this test should be using --implicit-check-not=error to prevent this from happening 

https://github.com/llvm/llvm-project/pull/96152