mailbox: sti: Fix module autoload for OF registration

If the driver is built as a module, autoload won't work because the module
alias information is not filled. So user-space can't match the registered
device with the corresponding module.

Export the module alias information using the MODULE_DEVICE_TABLE() macro.

Before this patch:

$ modinfo drivers/mailbox/mailbox-sti.ko | grep alias
alias:          platform:mailbox-sti

After this patch:

$ modinfo drivers/mailbox/mailbox-sti.ko | grep alias
alias:          platform:mailbox-sti
alias:          of:N*T*Cst,stih407-mailboxC*
alias:          of:N*T*Cst,stih407-mailbox

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/mailbox-sti.c

@@ -403,6 +403,7 @@ static const struct of_device_id sti_mailbox_match[] = {
 	},
 	{ }
 };
+MODULE_DEVICE_TABLE(of, sti_mailbox_match);
 
 static int sti_mbox_probe(struct platform_device *pdev)
 {