net: hns: Use IS_ERR_OR_NULL() helper function

Use the IS_ERR_OR_NULL() helper instead of open-coding a
NULL and an error pointer checks to simplify the code and
improve readability.

Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20240828122336.3697176-1-lihongbo22@huawei.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>