Fix subreg value numbers in handleMoveUp

The problem can occur in presence of subregs. If we are swapping two
instructions defining different subregs of the same register we will
get a new liveout from a block. We need to preserve value number for
block's liveout for successor block's livein to match.

Differential Revision: https://reviews.llvm.org/D30558

llvm-svn: 297534