MFC r217561:

MFC r217561:
For architectures not using direct map , and requiring real KVA page for
sf buf allocation, use wakeup() instead of wakeup_one() to notify sf
buffer waiters about free buffer.

sf_buf_alloc() calls msleep(PCATCH) when SFB_CATCH flag was given,
and for simultaneous wakeup and signal delivery, msleep() returns
EINTR/ERESTART despite the thread was selected for wakeup_one(). As
result, we loose a wakeup, and some other waiter will not be woken up.

git-svn-id: svn://svn.freebsd.org/base/stable/8@217816 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f