remove some serial drivers (rc, rp, cy)

[jmg]

Summary

These drivers were left behind in 2008 when the switch to
MPSAFE tty was done. They haven't been hooked up to the
build, and a couple of them still reference ttycreate which
doesn't exist anymore.

Test Plan

make universe
(to be done)

[jmg]

too smart w/ command line, include the rest of the files..

[phk]

Way overdue.

[jmg]

forgot to remove from files..

[jmg]

didn't complain about missing file on command line, that being
rp's module dir..

[0mp]

It looks like no manual pages reference those drivers anymore (checked with ag 'Xr (rc|rp|cy) 4')

[zeising]

Removed manual pages need to be added to ObsoleteFiles.inc as well.

[bcr]

All good from manpages.

[emaste]

Modules also need to be added to ObsoleteFiles.inc

[jmg]

In D25874#573062, @zeising wrote:

Removed manual pages need to be added to ObsoleteFiles.inc as well.

Thanks for the reminder. I thought of this, and then promptly forgot before doing it. :)

[jmg]

commited in https://reviews.freebsd.org/rS363683

Not sure why it didn't auto close.