[speculative-execution] Hoists debug values unnecessarily.

After https://reviews.llvm.org/D81730:
`SpeculativeExecutionPass::considerHoistingFromTo` hoists
instructions, including debug intrinsics, as long as none
of their used values are instructions that appear prior
in the block that are not being hoisted.

This behaviour has been duplicated for DPValues to get
rid of a binary difference.

The correct solution is not hoist these debug values at
all, whichever format they're in.

nit: Remove 'If' from comment.

Author: CarlosAlbertoEnciso

llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp

@@ -274,7 +274,7 @@ static InstructionCost ComputeSpeculationCost(const Instruction *I,
 //   call void @llvm.dbg.value(%x, !"x", !DIExpression())
 //   call void foo()
 //
-// If SpeculativeExecution might decide to hoist the 'y * z' calculation
+// SpeculativeExecution might decide to hoist the 'y * z' calculation
 // out of the 'if' block, because it is more efficient that way, so the
 // '%x = mul i32 %y, %z' moves to the block above. But it might also
 // decide to hoist the 'llvm.dbg.value' call.