net: hns: delete repeat read fbd num after while

Because we handle the received packets after napi, so delete the checking
before submitting. It delete the code of read the fbd number register,
which reduces the cpu usages while receiving packets

Signed-off-by: Daode Huang <huangdaode@hisilicon.com>
Reviewed-by: Yisen Zhuang <yisen.zhuang@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>