IB/hfi1: Add error checking for buffer overrun in OPA aggregate

Improve safety of code by checking the size of the data buffer and
prevent buffer overrun
Reviewed-by: NDennis Dalessandro <dennis.dalessandro@intel.com>
Reviewed-by: NBrian Welty <brian.welty@intel.com>
Signed-off-by: NNeel Desai <neel.desai@intel.com>
Signed-off-by: NDennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>