internal/lsp: fix return variables for FindPosInPackage
internal/lsp: fix return variables for FindPosInPackage

Change-Id: Icaa9595f05ab9583e60fc0392cbe21e1f20a3934
Reviewed-on: https://go-review.googlesource.com/c/tools/+/208666
Run-TryBot: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>
Reviewed-by: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools