net: wwan: qcom_bam_dmux: fix wrong pointer passed to IS_ERR()

It should check dmux->tx after calling dma_request_chan().

Fixes: 21a0ffd9 ("net: wwan: Add Qualcomm BAM-DMUX WWAN network driver")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20220319032450.3288224-1-yangyingliang@huawei.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/wwan/qcom_bam_dmux.c

@@ -755,7 +755,7 @@ static int __maybe_unused bam_dmux_runtime_resume(struct device *dev)
 		return 0;
 
 	dmux->tx = dma_request_chan(dev, "tx");
-	if (IS_ERR(dmux->rx)) {
+	if (IS_ERR(dmux->tx)) {
 		dev_err(dev, "Failed to request TX DMA channel: %pe\n", dmux->tx);
 		dmux->tx = NULL;
 		bam_dmux_runtime_suspend(dev);