MFC r264114, r264310, r268570:

r264114 by davidxu:

Fix SIGIO delivery. Use fsetown() to handle file descriptor owner
ioctl and use pgsigio() to send SIGIO.

r264310 by davidxu:

Add kqueue support for devctl.

r268570:

Clear nonblock and async on devctl close instaed of open.

This is a purely cosmetic change.