MFC r249466, r249481, r250025:

MFC r249466, r249481, r250025:
Remove multilevel freezing mechanism, implemented to handle specifics of
the ATA/SATA error recovery, when post-reset recovery commands should be
allocated when queues are already full of payload requests.  Instead of
removing frozen CCBs with specified range of priorities from the queue
to provide free openings, use simple hack, allowing explicit CCBs over-
allocation for requests with priority higher (numerically lower) then
CAM_PRIORITY_OOB threshold.

Simplify CCB allocation logic by removing SIM-level allocation queue.
After that SIM-level queue manages only CCBs execution, while allocation
logic is localized within each single device.

git-svn-id: svn://svn.freebsd.org/base/stable/9@256216 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f