Increase device openings to tagged maximum.

Increase device openings to tagged maximum.

Some SIMs report much less untagged device openings then tagged ones.
Target mode devices are not handled by regular probing routines, and so
there is nothing to increase queue size for them to the SIM's maximum.
To fix that resize the queue explicitly on ctl periph registration.
This radically improves performance of mpt(4) in target mode.

Also fetch and report device queue statistics in `ctladm dumpstructs`,
since regular way of `camcontrol tags` is not usable in target mode.

MFC after:	2 weeks