ARM: OMAP: fix iommu, not mailbox

For some weird (freudian?) reason, commit 435792d "ARM: OMAP: make
iommu subsys_initcall to fix builtin omap3isp" unintentionally changed
the mailbox's initcall instead of the iommu's.

Fix that.

Reported-by: Fernando Guzman Lugo <fernando.lugo@ti.com>
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Joerg Roedel <Joerg.Roedel@amd.com>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
diff --git a/arch/arm/mach-omap2/mailbox.c b/arch/arm/mach-omap2/mailbox.c
index a6db1e4..609ea2d 100644
--- a/arch/arm/mach-omap2/mailbox.c
+++ b/arch/arm/mach-omap2/mailbox.c
@@ -412,8 +412,7 @@
 	platform_driver_unregister(&omap2_mbox_driver);
 }
 
-/* must be ready before omap3isp is probed */
-subsys_initcall(omap2_mbox_init);
+module_init(omap2_mbox_init);
 module_exit(omap2_mbox_exit);
 
 MODULE_LICENSE("GPL v2");