[PECOFF] Skip a section if there's no atom in the section.

Some sections, such as with IMAGE_SCN_LNK_REMOVE attribute, is skipped
in the first pass. Such sections need to be skipped in the latter passes.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@187281 91177308-0d34-0410-b5e6-96231b3b80d8