hpsa: correct compiler warnings introduced by hpsa-add-local-workqueue patch

Correct compiler warning introduced by hpsa-add-local-workqueue patch
6636e7f4 hpsa: Use local workqueues
instead of system workqueues

Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Scott Teel <scott.teel@pmcs.com>
Reviewed-by: Webb Scales <webbnh@hp.com>
Signed-off-by: Don Brace <don.brace@pmcs.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>