cerbero: Add PEM certs as a `file` filetype
cerbero: Add PEM certs as a `file` filetype

The latest version of file reports .crt files as a PEM certificate
instead of a generic text file. Also remove duplicate 'data' entry.

Fixes the ios-universal build on macOS 10.12

atsushieno/cerbero,flexVDI/cerbero,GStreamer/cerbero,GStreamer/cerbero,OptoFidelity/cerbero,GStreamer/cerbero,flexVDI/cerbero,nirbheek/cerbero,GStreamer/cerbero,fluendo/cerbero,nirbheek/cerbero,atsushieno/cerbero,OptoFidelity/cerbero,centricular/cerbero,centricular/cerbero,atsushieno/cerbero,atsushieno/cerbero,nirbheek/cerbero,flexVDI/cerbero,centricular/cerbero,atsushieno/cerbero,justinjoy/cerbero,OptoFidelity/cerbero,EricssonResearch/cerbero,centricular/cerbero,flexVDI/cerbero,flexVDI/cerbero,justinjoy/cerbero,EricssonResearch/cerbero,GStreamer/cerbero,EricssonResearch/cerbero,justinjoy/cerbero,EricssonResearch/cerbero,justinjoy/cerbero,fluendo/cerbero,fluendo/cerbero,fluendo/cerbero,centricular/cerbero,fluendo/cerbero,nirbheek/cerbero,OptoFidelity/cerbero,EricssonResearch/cerbero