[SLP] Update the debug based on Michael's suggestion.

Passing the types/opcode check still doesn't guarantee we'll actually vectorize.
Therefore, just make it clear we're attempting to vectorize.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280263 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed