There is a mixture of mutex and spinlocks to protect receive context
(rcd/uctxt) information.  This is not used consistently.

Use the mutex to protect device receive context information only.
Use the spinlock to protect sub context information only.

Protect access to items in the rcd array with a spinlock and
reference count.

Remove spinlock around dd->rcd array cleanup.  Since interrupts are
disabled and cleaned up before this point, this lock is not useful.
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-by: Sebastian Sanchez <sebastian.sanchez@intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>