disp: msm: make msm_drm into single module

Make msm_drm into single module and all child driver
registers and unregisters are handled from parent's
register and unregister respectively.

Change-Id: I017513d1de3b6b25dd5543d7fa7741c0bac1740d
Signed-off-by: Shashank Babu Chinta Venkata <sbchin@codeaurora.org>
Signed-off-by: Narendra Muppalla <NarendraM@codeaurora.org>
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>

msm/sde/sde_wb.c

@@ -824,15 +824,12 @@ static struct platform_driver sde_wb_driver = {
 	},
 };
 
-static int __init sde_wb_register(void)
+void __init sde_wb_register(void)
 {
-	return platform_driver_register(&sde_wb_driver);
+	platform_driver_register(&sde_wb_driver);
 }
 
-static void __exit sde_wb_unregister(void)
+void __exit sde_wb_unregister(void)
 {
 	platform_driver_unregister(&sde_wb_driver);
 }
-
-module_init(sde_wb_register);
-module_exit(sde_wb_unregister);