[GVNHoist] Mark GlobalsAA as preserved by GVNHoist.

Reviewers: sebpop, hiraditya

Reviewed By: sebpop

Subscribers: n.bozhenov, llvm-commits

Differential Revision: https://reviews.llvm.org/D32158
Patch by Andrei Elovikov <andrei.elovikov@intel.com>

llvm-svn: 300552