[llvm] MIPS/Asm/O32: Don't add another $ to PrivateGlobal symbol (PR #80644)

[Fangrui Song via llvm-commits]

================
@@ -0,0 +1,23 @@
+# RUN: llvm-mc %s -triple=mips-unknown-linux -show-encoding -mcpu=mips32r2 | \
+# RUN:   FileCheck %s --check-prefixes=CHECK
+# RUN: llvm-mc %s -triple=mips-unknown-linux -show-encoding -mcpu=mips32r6 | \
+# RUN:   FileCheck %s --check-prefixes=CHECK
+
+	.text
+	.abicalls
+	.option	pic2
+xx:
+	la	$2,.Lhello #CHECK: lw      $2, %got(.Lhello)($gp)          # encoding: [0x8f,0x82,A,A]
----------------
MaskRay wrote:

```
# CHECK:      lw ...
# CHECK-NEXT:   fixup A ...
# CHECK-NEXT:   ...
la $2, $hello2
```

https://github.com/llvm/llvm-project/pull/80644