remoteproc: imx_dsp_rproc: Improve exception handling in imx_dsp_rproc_mbox_alloc()

The label “err_out” was used to jump to another pointer check
despite of the detail in the implementation of the function
“imx_dsp_rproc_mbox_alloc” that it was determined already
that the corresponding variable contained an error pointer
because of a failed call of the function “mbox_request_channel_byname”.

Thus perform the following adjustments:

1. Return directly after a call of the function
   “mbox_request_channel_byname” failed for the input parameter “tx”.

2. Use more appropriate labels instead.

3. Reorder jump targets at the end.

4. Omit a function call and three extra checks.

This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Link: https://lore.kernel.org/r/d0e18bb1-afc4-8b6f-bb1c-b74b3bad908e@web.deSigned-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

drivers/remoteproc/imx_dsp_rproc.c

@@ -530,7 +530,7 @@ static int imx_dsp_rproc_mbox_alloc(struct imx_dsp_rproc *priv)
 		ret = PTR_ERR(priv->tx_ch);
 		dev_dbg(cl->dev, "failed to request tx mailbox channel: %d\n",
 			ret);
-		goto err_out;
+		return ret;
 	}
 
 	/* Channel for receiving message */
@@ -539,7 +539,7 @@ static int imx_dsp_rproc_mbox_alloc(struct imx_dsp_rproc *priv)
 		ret = PTR_ERR(priv->rx_ch);
 		dev_dbg(cl->dev, "failed to request rx mailbox channel: %d\n",
 			ret);
-		goto err_out;
+		goto free_channel_tx;
 	}
 
 	cl = &priv->cl_rxdb;
@@ -555,19 +555,15 @@ static int imx_dsp_rproc_mbox_alloc(struct imx_dsp_rproc *priv)
 		ret = PTR_ERR(priv->rxdb_ch);
 		dev_dbg(cl->dev, "failed to request mbox chan rxdb, ret %d\n",
 			ret);
-		goto err_out;
+		goto free_channel_rx;
 	}
 
 	return 0;
 
-err_out:
-	if (!IS_ERR(priv->tx_ch))
-		mbox_free_channel(priv->tx_ch);
-	if (!IS_ERR(priv->rx_ch))
-		mbox_free_channel(priv->rx_ch);
-	if (!IS_ERR(priv->rxdb_ch))
-		mbox_free_channel(priv->rxdb_ch);
-
+free_channel_rx:
+	mbox_free_channel(priv->rx_ch);
+free_channel_tx:
+	mbox_free_channel(priv->tx_ch);
 	return ret;
 }