RDMA/hns: Fix the counting error of bonding with more than 2 slaves

driver inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6ZACP



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When changeupper event happens involving bond group with more than 2
slaves, the counting of slave num is incorrect for the reason that there
are no corresponding hr_dev for uninited slaves, which leads to the
failure in adding 3 or more slaves to a bond group.

Applying this patch, the counting begins from the previous value but not
0, and updates slave_map and slave_map_diff depending on whether slave
num increases or decreases. Besides, since bond_grp->slave_num is no
longer used, remove it.

Fixes: e62a2027 ("RDMA/hns: support RoCE bonding")
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>