IB/hfi1: Do not read more than a SGE length

In certain cases, if the tail of an SGE is not
8-byte aligned, bytes beyond the end to an 8-byte
alignment can be read. Change the copy routine
to avoid the over-read. Instead, stop on the final
whole quad-word, then read the remaining bytes.

Reviewed-by: Dean Luick <dean.luick@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>