IB/hfi1: Allow MgmtAllowed on B2B setups

HFI's are hard-wired to send Device Info frames with
MgmtAllowed bit set to 0. This means in B2B setups,
MgmtAllowed would never be allowed, which prevents
remote opa management tools from working properly.

Assume MgmtAllowed if a neighbor is also an HFI.

Fixes: 98b9ee20 ("IB/hfi1: Cache neighbor secure data after link up")
Reviewed-by: Sebastian Sanchez <sebastian.sanchez@intel.com>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Jan Sokolowski <jan.sokolowski@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>