Remove overuse of exclamation marks in kernel printfs, there mere fact a
message has been printed is enough to get someones attention. Also remove the
line number for DPRINTF/DPRINTFN, it already prints the funtion name and a
unique message.
It is possible for all the kthreads to exit (hci modules unloaded) which in
turn ends our usb process. This means the proc pointer becomes invalid and will
panic if a new kthread is added. Count the number of threads and clear the proc
pointer on the last one.
Approved by: re (kib)
Change the usb workers from kernel processes to threads, this is mostly a
cosmetic change to reduce cruft in the proc table.
Also change the idle wait message to `-` like how taskqueues are.
Reviewed by: julian
Approved by: re (kib)