[GVNHoist] Fix: PR35222 gvn-hoist incorrectly erases load

w.r.t. the paper
"A Practical Improvement to the Partial Redundancy Elimination in SSA Form"
(https://sites.google.com/site/jongsoopark/home/ssapre.pdf)

Proper dominance check was missing here, so having a loopinfo should not be required.
Committing this diff as this fixes the bug, if there are
further concerns, I'll be happy to work on them.

Differential Revision: https://reviews.llvm.org/D39781

llvm-svn: 320607