[LLVMGPU] Cleanup VirtualMMA functions to match refactoring on base MMAAttr #31810

Job	Run time
setup / setup	9s
runtime_small	2m 5s
runtime :: ubuntu-20.04	1m 30s
runtime :: windows-2022	3m 29s
runtime_tracing :: tracy provider	1m 30s
runtime :: macos-14	1m 28s
runtime_tracing :: console provider	1m 28s
summary	6s
	11m 45s

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