[oe] meta-browser duplicate patch

[Trevor Woerner]

Does the do_patch logic now ignore the same patch being applied twice? I was
quite sure this was a problem in the past (and if it isn't, maybe it should
be?)

In commit fb4e542079958b6afde324a1e9bfdd695842aeeb
the patch recipes-browser/chromium/chromium/chromium/Do-not-depend-on-Linux-4.5.patch

and in commit c6fc9da7be64af7cd08c2bbb026e4c3ffc760687
the patch recipes-browser/chromium/chromium/chromium/unset-madv-free.patch

are exactly the same. Yet they're both happily applied without so much as a
warning, not even in temp/log.do_patch.