[openmp] Use llvm GridValues from devicertl

Add include path to the cmakefiles and set the target_impl enums
from the llvm constants instead of copying the values.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D108391

GitOrigin-RevId: 842f875c8b38ea46dfb973a062585889cc60d277
6 files changed