net: hns: fix length and 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 length and page_offset are u16, they will
overflow. So change them to u32.

Fixes: 6fe6611f

 ("net: add Hisilicon Network Subsystem hnae framework support")
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>