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 <[e-mail]>
Reviewed-by: Jacob Keller <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ethernet/hisilicon/hns/hns_dsaf_mac.c

···
 		return -ENODATA;
 
 	phy = get_phy_device(mdio, addr, is_c45);
-	if (!phy || IS_ERR(phy))
+	if (IS_ERR_OR_NULL(phy))
 		return -EIO;
 
 	phy->irq = mdio->irq[addr];