staging/rdma/hfi1: Add a schedule in send thread

When under heavy load, the send handler can run too long without allowing other
tasks to run.  Add a conditional resched to break this up.

Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Dean Luick <dean.luick@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>