spi: spi-s3c64xx: Use module_platform_driver()

subsys_init_call() initializes driver too early.
It's preventing to move DMA channel allocation at the begining
(driver probe).

This patch reduces and simplifies initalization code by
using module_platform_driver() macro.
It's also efficiently delaying driver startup.

Signed-off-by: Lukasz Czerwinski <l.czerwinski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/spi/spi-s3c64xx.c

@@ -1633,22 +1633,13 @@ static struct platform_driver s3c64xx_spi_driver = {
 		.pm = &s3c64xx_spi_pm,
 		.of_match_table = of_match_ptr(s3c64xx_spi_dt_match),
 	},
+	.probe = s3c64xx_spi_probe,
 	.remove = s3c64xx_spi_remove,
 	.id_table = s3c64xx_spi_driver_ids,
 };
 MODULE_ALIAS("platform:s3c64xx-spi");
 
-static int __init s3c64xx_spi_init(void)
-{
-	return platform_driver_probe(&s3c64xx_spi_driver, s3c64xx_spi_probe);
-}
-subsys_initcall(s3c64xx_spi_init);
-
-static void __exit s3c64xx_spi_exit(void)
-{
-	platform_driver_unregister(&s3c64xx_spi_driver);
-}
-module_exit(s3c64xx_spi_exit);
+module_platform_driver(s3c64xx_spi_driver);
 
 MODULE_AUTHOR("Jaswinder Singh <jassi.brar@samsung.com>");
 MODULE_DESCRIPTION("S3C64XX SPI Controller Driver");