staging/rdma/hfi1: Destroy workqueues if hfi1_register_ib_device() call returns error

Currently, if hfi1_register_ib_device() call is unsuccessful, workqueues
are not being destroyed before bailing out. This patch fixes this issue.

Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Harish Chegondi <harish.chegondi@intel.com>
Signed-off-by: Jubin John <jubin.john@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>