Make camcontrol identify work with nda devices

Both ATA and NVME have an identify command. They are completely
different, but to the user they are the same. Leverage nvmecontrol's
print_controller code to provide that functionality to camcontrol
identify. Query the path to see what kind of protocol it supports, and
send the most appropriate command down. Refactor nvme_print_dev a
little to make it easy to get the nvme cdata.

Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D15371