Fix PR16110: Handle DBG_VALUE in ConnectedVNInfoEqClasses::Distribute().

Now that the LiveDebugVariables pass is running *after* register
coalescing, the ConnectedVNInfoEqClasses class needs to deal with
DBG_VALUE instructions.

This only comes up when rematerialization during coalescing causes the
remaining live range of a virtual register to separate into two
connected components.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182592 91177308-0d34-0410-b5e6-96231b3b80d8