dmaengine: mxs: use platform_driver_register

Driver registration fails on SOC imx8mn as its supplier, the clock
control module, is probed later than subsys initcall level. This driver
uses platform_driver_probe which is not compatible with deferred probing
and won't be probed again later if probe function fails due to clock not
being available at that time.

This patch replaces the use of platform_driver_probe with
platform_driver_register which will allow probing the driver later again
when the clock control module will be available.

The __init annotation has been dropped because it is not compatible with
deferred probing. The code is not executed once and its memory cannot be
freed.

Fixes: a580b8c5 ("dmaengine: mxs-dma: add dma support for i.MX23/28")
Co-developed-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Cc: stable@vger.kernel.org

Link: https://lore.kernel.org/r/20220921170556.1055962-1-dario.binacchi@amarulasolutions.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/mxs-dma.c

@@ -670,7 +670,7 @@ static enum dma_status mxs_dma_tx_status(struct dma_chan *chan,
 	return mxs_chan->status;
 }
 
-static int __init mxs_dma_init(struct mxs_dma_engine *mxs_dma)
+static int mxs_dma_init(struct mxs_dma_engine *mxs_dma)
 {
 	int ret;
 
@@ -741,7 +741,7 @@ static struct dma_chan *mxs_dma_xlate(struct of_phandle_args *dma_spec,
 				     ofdma->of_node);
 }
 
-static int __init mxs_dma_probe(struct platform_device *pdev)
+static int mxs_dma_probe(struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
 	const struct mxs_dma_type *dma_type;
@@ -839,10 +839,7 @@ static struct platform_driver mxs_dma_driver = {
 		.name	= "mxs-dma",
 		.of_match_table = mxs_dma_dt_ids,
 	},
+	.probe = mxs_dma_probe,
 };
 
-static int __init mxs_dma_module_init(void)
-{
-	return platform_driver_probe(&mxs_dma_driver, mxs_dma_probe);
-}
-subsys_initcall(mxs_dma_module_init);
+builtin_platform_driver(mxs_dma_driver);