[OPENMP][OFFLOADING]Change the lambda capturing flags.

Summary:
The previously used combination `PTR_AND_OBJ | PRIVATE` could be used
for mapping of some data in Fortran. Changed it to `PTR_AND_OBJ |
  LITERAL`.

Reviewers: gtbercea

Subscribers: guansong, caomhin, openmp-commits

Differential Revision: https://reviews.llvm.org/D54035

llvm-svn: 345981