mtd: convert drivers/mtd/* to use module_platform_driver()

This patch converts the drivers in drivers/mtd/* to use the
module_platform_driver() macro which makes the code smaller and a bit
simpler.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/drivers/mtd/maps/rbtx4939-flash.c b/drivers/mtd/maps/rbtx4939-flash.c
index 0237f19..bb7d204 100644
--- a/drivers/mtd/maps/rbtx4939-flash.c
+++ b/drivers/mtd/maps/rbtx4939-flash.c
@@ -137,18 +137,7 @@
 	},
 };
 
-static int __init rbtx4939_flash_init(void)
-{
-	return platform_driver_register(&rbtx4939_flash_driver);
-}
-
-static void __exit rbtx4939_flash_exit(void)
-{
-	platform_driver_unregister(&rbtx4939_flash_driver);
-}
-
-module_init(rbtx4939_flash_init);
-module_exit(rbtx4939_flash_exit);
+module_platform_driver(rbtx4939_flash_driver);
 
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("RBTX4939 MTD map driver");