iommu/msm: Use standard driver registration

It's been a long time since there was any reason to register IOMMU
drivers early. Convert to the standard platform driver helper.

CC: Andy Gross <agross@kernel.org>
CC: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/all/05ca5e1b29bdd350f4e20b9ceb031a2c281e23d2.1644005728.git.robin.murphy@arm.com/
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: rmurphy-arm

drivers/iommu/msm_iommu.c

@@ -831,16 +831,4 @@ static struct platform_driver msm_iommu_driver = {
 	.probe		= msm_iommu_probe,
 	.remove		= msm_iommu_remove,
 };
-
-static int __init msm_iommu_driver_init(void)
-{
-	int ret;
-
-	ret = platform_driver_register(&msm_iommu_driver);
-	if (ret != 0)
-		pr_err("Failed to register IOMMU driver\n");
-
-	return ret;
-}
-subsys_initcall(msm_iommu_driver_init);
-
+builtin_platform_driver(msm_iommu_driver);