IB/hfi1: Fix memory leak in exception path in get_irq_affinity()

When IRQ affinity is set and the interrupt type is unknown, a cpu
mask allocated within the function is never freed. Fix this memory
leak by allocating memory within the scope where it is used.

Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Sebastian Sanchez <sebastian.sanchez@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>