RDMA/hns: Fix the counting error of slave number

driver inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6Z4E9



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Currently, the driver will count the number of slave hr_dev,
but during bond clearing event and slave decreasing event, only
one slave has a corresponding hr_dev, and the number will always
be 1. It causes that all slave decrease events are redirected to
a bond clearing operation.

This patch fixes this problem by counting slave netdev directly instead
of getting its hr_dev during bond clearing event and slave decreasing
event.

Fixes: 646b97db ("RDMA/hns: adjust the structure of RoCE bonding driver")
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>