IB/hfi1: Fix to fully initialize send context area

While handling buffer control MAD, partially initialized
dd->kernel_send_context area may cause potential dereference
of uninitialized pointers. Fix by using kzalloc_node()
instead of kmalloc_node().

Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Reviewed-by: Andrzej Kacprowski <andrzej.kacprowski@intel.com>
Signed-off-by: Tymoteusz Kielan <tymoteusz.kielan@intel.com>
Signed-off-by: Andrzej Kacprowski <andrzej.kacprowski@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>