Revert "[NVPTX] Disable parens for identifiers starting with '$'"

This reverts commit 78d70a1c.

Failed on Mips32:
https://lab.llvm.org/buildbot#builders/109/builds/36628

   # CHECK: # fixup A - offset: 0, value: ($tmp0), kind: fixup_Mips_26
   <stdin>:580:2: note: possible intended match here
   # fixup A - offset: 0, value: $tmp0, kind: fixup_Mips_26