[DWARF] Handle the DW_OP_entry_value operand

Add the IR and the AsmPrinter parts for handling of the DW_OP_entry_values
DWARF operation.

([11/13] Introduce the debug entry values.)

Co-authored-by: Ananth Sowda <asowda@cisco.com>
Co-authored-by: Nikola Prica <nikola.prica@rt-rk.com>
Co-authored-by: Ivan Baev <ibaev@cisco.com>

Differential Revision: https://reviews.llvm.org/D60866

llvm-svn: 364542