IB/core: Avoid SGID attributes query while converting GID from OPA to IB

SGID attributes are not used during OPA to IB GID conversion.
Therefore don't query it.

Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>