For user applications that use UD QPs, always resolve destination MAC
from the GRH.  This is to avoid failure due to any garbage value in
the attr->dmac.
Signed-off-by: Selvin Xavier <selvin.xavier@emulex.com>
Signed-off-by: Devesh Sharma <devesh.sharma@emulex.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>