MFC r264114, r264310, r268570:
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.

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