[llvm] [LoongArch] Enable FeatureExtLSX for generic-la64 processor (PR #113421)

[Lu Weining via llvm-commits]

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@@ -1,3 +1,4 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
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SixWeining wrote:

The checking prefixes for this test were written manually. I prefer keeping this style unchanged this time for easy-reviewing. Then maybe you can submit a separate `NFC` PR switching to use `update_llc_test_checks.py`.

https://github.com/llvm/llvm-project/pull/113421