[IRPrinting] Improve module pass printer to work better with -filter-print-funcs

Summary: Previously module pass printer pass prints the banner even when the module doesn't include any function provided with `-filter-print-funcs` option. This introduced a lot of noise, especailly with ThinLTO. This diff addresses the issue and makes the banner printed only when the module includes functions in `-filter-print-funcs` list.

Reviewers: fedor.sergeev

Subscribers: mehdi_amini, hiraditya, dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66560

llvm-svn: 370849