Get rid of the 'chan' from softc structure and use the latter
directly as sleep channel.

PR:		kern/174684
Submitted by:	jmg
MFC after:	2 weeks

git-svn-id: svn+ssh://svn.freebsd.org/base/head@262572 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
(cherry picked from commit 3cb8666b931e8e49fabbd097c1f7cb38806c22cb)