Revert "[InstCombine] Drop debug loc in TryToSinkInstruction"

This reverts commit 903cf140.

This might be causing verifier failures on the bots, such as: "inlinable
function call in a function with debug info must have a !dbg location"
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http://lab.llvm.org:8011/builders/sanitizer-ppc64be-linux/builds/16976/steps/bootstrap%20clang/logs/stdio