Fix non-affine generated entering node not being recognized as dominating

Scalar reloads in the generated entering block were not recognized as
dominating the subregions locks when there were multiple entering
nodes. This resulted in values defined in there not being copied.

As a fix, we unconditionally add the BBMap of the generated entering
node to the generated entry. This fixes part of llvm.org/PR25439.

llvm-svn: 252445