[llvm] [Mips] Fix inst `sc` disassemble assert when configured -mattr=+ptr64 (PR #158253)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,3 @@
+# RUN: llvm-mc -triple=mips64el-unknown-linux -disassemble -mattr=+ptr64 -mcpu=mips3 %s | FileCheck %s
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arsenm wrote:

Test belongs in test/MC/Disassembler/Mips (Also, it shouldn't really be necessary to manually specify ptr64)

https://github.com/llvm/llvm-project/pull/158253