[Flang][OpenMP][Parser] Resolve Declare Target Directive Symbols

Currently symbols are not resolved for declare target
after they've been modified by prior passes. This can
lead to missing or incorrect symbols in subsequent
compiler phases when declare target is used with
more complex types e.g. common block.

This patch should allow these symbols to be
resolved appropriately.

Reviewers: kiranchandramohan

Differential Revision: https://reviews.llvm.org/D151993