Dropping common.h usage

Hey all,

Now that checkpatch.pl complains about adding common.h to new files, I would like to ask custodians to try and fixup patches that had been submitted already and use the header. In general, we can just drop the file entirely. If we can't it's often a quick fix of which include file was missing already. If it's a mess to unwind, that's another matter of course. Thanks!