RDMA/device: Remove optimization in ib_device_get_netdev()

The caller of ib_device_get_netdev() relies on its result to accurately
match a given netdev with the ib device associated netdev.

ib_device_get_netdev returns NULL when the IB device associated
netdev is unregistering, preventing the caller of matching netdevs properly.

Thus, remove this optimization and return the netdev even if
it is undergoing unregistration, allowing matching by the caller.

This change ensures proper netdev matching and reference count handling
by the caller of ib_device_get_netdev/ib_device_set_netdev API.

Signed-off-by: Maher Sanalla <msanalla@nvidia.com>
Signed-off-by: Chiara Meiohas <cmeiohas@nvidia.com>
Signed-off-by: Michael Guralnik <michaelgur@nvidia.com>
Link: https://patch.msgid.link/20240909173025.30422-5-michaelgur@nvidia.com
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/core/device.c

@@ -2252,15 +2252,6 @@ struct net_device *ib_device_get_netdev(struct ib_device *ib_dev,
 		spin_unlock(&pdata->netdev_lock);
 	}
 
-	/*
-	 * If we are starting to unregister expedite things by preventing
-	 * propagation of an unregistering netdev.
-	 */
-	if (res && res->reg_state != NETREG_REGISTERED) {
-		dev_put(res);
-		return NULL;
-	}
-
 	return res;
 }