[llvm] [AArch64][SME] Use reportFatalUsageError rather than assert (NFC) (PR #145491)

[Matt Arsenault via llvm-commits]

================
@@ -481,7 +481,8 @@ AArch64TargetMachine::getSubtargetImpl(const Function &F) const {
         MaxSVEVectorSize, IsStreaming, IsStreamingCompatible, HasMinSize);
   }
 
-  assert((!IsStreaming || I->hasSME()) && "Expected SME to be available");
+  if (IsStreaming && !I->hasSME())
+    reportFatalUsageError("Streaming SVE functions require SME");
----------------
arsenm wrote:

```suggestion
    reportFatalUsageError("streaming SVE functions require SME");
```

https://github.com/llvm/llvm-project/pull/145491