RDMA/hns: Fix unnecessary port_num transition in HW stats allocation

RDMA/hns: Fix unnecessary port_num transition in HW stats allocation

[ Upstream commit b4a797b894dc91a541ea230db6fa00cc74683bfd ]

The num_ports capability of devices should be compared with the
number of port(i.e. the input param "port_num") but not the port
index(i.e. port_num - 1).

Fixes: 5a87279591a1 ("RDMA/hns: Support hns HW stats")
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Link: https://lore.kernel.org/r/20231017125239.164455-7-huangjunxian6@hisilicon.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>