can we drop the comedi serial2002 drivers from staging?

[Christoph Hellwig]

As far as I can tell there has been no targeted work on the driver
since merging it at all, and since 2014 even the comedi-wide
cleanups stopped, laving just drive by tree wide changes since.

At the same time the driver badly abuses the tty layer and is one
of only two major abusers of the poll code for in-kernel waits.