[Debuginfo][Instcombiner] Do not clone dbg.declare.

TryToSinkInstruction() has a bug: While updating debug info for
sunk instruction, it could clone dbg.declare intrinsic.
That is wrong. There could be only one dbg.declare.
The fix is to not clone dbg.declare intrinsic and to update
it`s arguments, to not to point to sunk instruction.

Differential Revision: https://reviews.llvm.org/D67217

llvm-svn: 371587