net: hns3: fix page_offset overflow when CONFIG_ARM64_64K_PAGES

When enable the config item "CONFIG_ARM64_64K_PAGES", the size of
PAGE_SIZE is 65536(64K). But the type of page_offset is u16, it will
overflow. So change it to u32, when "CONFIG_ARM64_64K_PAGES" enabled.

Fixes: 76ad4f0e

 ("net: hns3: Add support of HNS3 Ethernet Driver for hip08 SoC")
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>