IB/core: Use GRH when the path hop-limit > 0

IB/core: Use GRH when the path hop-limit > 0

commit 11d8d645343efba0c975aefe7c2cf3b33c836c75 upstream.

According to IBTA spec v1.3 section 12.7.19, QPs should use GRH when
the path returned by the SA has hop-limit > 0. Currently, we do that
only for the > 1 case, fix that.

Fixes: 6d969a471ba1 ('IB/sa: Add ib_init_ah_from_path()')
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>