uio: remove unneeded variable "ret" in uio_dmem_genirq_open

Fix the following coccicheck warning:

drivers/uio/uio_dmem_genirq.c:47:5-8: Unneeded variable: "ret". Return
"0" on line 71
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Link: https://lore.kernel.org/r/20200428063155.42349-1-yanaijie@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/uio/uio_dmem_genirq.c

@@ -44,7 +44,6 @@ static int uio_dmem_genirq_open(struct uio_info *info, struct inode *inode)
 {
 	struct uio_dmem_genirq_platdata *priv = info->priv;
 	struct uio_mem *uiomem;
-	int ret = 0;
 	int dmem_region = priv->dmem_region_start;
 
 	uiomem = &priv->uioinfo->mem[priv->dmem_region_start];
@@ -68,7 +67,7 @@ static int uio_dmem_genirq_open(struct uio_info *info, struct inode *inode)
 	mutex_unlock(&priv->alloc_lock);
 	/* Wait until the Runtime PM code has woken up the device */
 	pm_runtime_get_sync(&priv->pdev->dev);
-	return ret;
+	return 0;
 }
 
 static int uio_dmem_genirq_release(struct uio_info *info, struct inode *inode)