RDMA/core: Modify rdma_query_gid() to return accurate error codes

Modify rdma_query_gid() to return -ENOENT for empty entries. This will
make error reporting more accurate and will be used in next patches.

Link: https://lore.kernel.org/r/1f2b65dfb4d995e74b621e3e21e7c7445d187956.1639055490.git.leonro@nvidia.com


Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Mark Zhang <markzhang@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>