[ASMPrinter] Fix missing handling of DW_OP_bit_piece

In r256077, I added printing for DIExpressions in DEBUG_VALUE comments,
but neglected to handle DW_OP_bit_piece operands. Thanks to
Mikael Holmen and Joerg Sonnenberger for spotting this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@256236 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed