mailbox: drop owner assignment from platform_drivers

A platform_driver does not need to set an owner, it will be populated by the
driver core.

Signed-off-by: Wolfram Sang <[e-mail]>

drivers/mailbox/omap-mailbox.c

···
 	.remove	= omap_mbox_remove,
 	.driver	= {
 		.name = "omap-mailbox",
-		.owner = THIS_MODULE,
 		.of_match_table = of_match_ptr(omap_mailbox_of_match),
 	},
 };