[OPENMP] Capture argument of `device` clause for target-based

[OPENMP] Capture argument of `device` clause for target-based
directives.

The argument of the `device` clause in target-based executable
directives must be captured to support codegen for the `target`
directives with the `depend` clauses.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@314686 91177308-0d34-0410-b5e6-96231b3b80d8