staging: unisys: Fix CamelCase for Disk Add/Remove global variables in virthba.c

This patch fixes the Disk Add/Remove (DAR) related CamelCase global
variables in virthba.c, reported by the checkpatch script:
  DARWorkQ --> dar_work_queue
  DARWorkQHead --> dar_work_queue_head
  DARWorkQLock --> dar_work_queue_lock
  DARWorkQSched --> dar_work_queue_sched

Signed-off-by: Ken Depro <kenneth.depro@unisys.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>