wifi: ath11k: fix return value check in ath11k_ahb_probe()

ioremap() returns NULL pointer not PTR_ERR() when it fails,
so replace the IS_ERR() check with NULL pointer check.

Fixes: b42b3678 ("wifi: ath11k: remap ce register space for IPQ5018")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230217030031.4021289-1-yangyingliang@huawei.com

drivers/net/wireless/ath/ath11k/ahb.c

@@ -1174,7 +1174,7 @@ static int ath11k_ahb_probe(struct platform_device *pdev)
 		 * to a new space for accessing them.
 		 */
 		ab->mem_ce = ioremap(ce_remap->base, ce_remap->size);
-		if (IS_ERR(ab->mem_ce)) {
+		if (!ab->mem_ce) {
 			dev_err(&pdev->dev, "ce ioremap error\n");
 			ret = -ENOMEM;
 			goto err_core_free;