[llvm] [ARM] Move MCStreamer::emitThumbFunc to ARMTargetStreamer (PR #126199)

[Peter Smith via llvm-commits]

================
@@ -168,6 +168,7 @@ class ARMTargetStreamer : public MCTargetStreamer {
 
   virtual void annotateTLSDescriptorSequence(const MCSymbolRefExpr *SRE);
 
+  virtual void emitThumbFunc(MCSymbol *Symbol);
----------------
smithp35 wrote:

Could we preserve the comment, minus the ARM only part
```
Note in the output that the specified \p Func is a Thumb mode function.
```

https://github.com/llvm/llvm-project/pull/126199