RDMA: Introduce and use rdma_device_to_ibdev()

Introduce and use rdma_device_to_ibdev() API for those drivers which are
registering one sysfs group and also use in ib_core.

In subsequent patch, device->provider_ibdev one-to-one mapping is no
longer holds true during accessing sysfs entries.
Therefore, introduce an API rdma_device_to_ibdev() that provides such
information.

Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/i40iw/i40iw_verbs.c

@@ -2139,9 +2139,8 @@ static int i40iw_dereg_mr(struct ib_mr *ib_mr)
 static ssize_t hw_rev_show(struct device *dev,
 			   struct device_attribute *attr, char *buf)
 {
-	struct i40iw_ib_device *iwibdev = container_of(dev,
-						       struct i40iw_ib_device,
-						       ibdev.dev);
+	struct i40iw_ib_device *iwibdev =
+		rdma_device_to_drv_device(dev, struct i40iw_ib_device, ibdev);
 	u32 hw_rev = iwibdev->iwdev->sc_dev.hw_rev;
 
 	return sprintf(buf, "%x\n", hw_rev);