net: hns3: fix statistics issue when disable page pool

driver inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8ISOD


CVE: NA

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It shouldn't update the page pool statistics when page pool
is disabled, which may cause statistics overlap.

Fixes: 59de65f6 ("net: hns3: add support for page_pool_get_stats")
Signed-off-by: Jian Shen <shenjian15@huawei.com>