IB/core: Updating cache for subnet_prefix in config_non_roce_gid_cache()

IB/core: Updating cache for subnet_prefix in config_non_roce_gid_cache()

Currently, cache for subnet_prefix was getting updated by reading port
attributes via ib_query_port. ib_query_port() calls ops.query_gid() to get
subnet_prefix and returns it via port_attr.

In ib_cache_update(), config_non_roce_gid_cache() obtains GIDs by calling
ops.query_gid(). We utilize this to store subnet_prefix in cache.

Link: https://lore.kernel.org/r/20210712122625.1147-2-anand.a.khoje@oracle.com
Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Suggested-by: Aru Kolappan <aru.kolappan@oracle.com>
Signed-off-by: Anand Khoje <anand.a.khoje@oracle.com>
Signed-off-by: Haakon Bugge <haakon.bugge@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>