mailbox: mailbox-test: rename driver as generic test driver

This mailbox-test driver was designed to be generic, so let's remove ST
tag on it and make it generic.
Acked-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NSudeep Holla <sudeep.holla@arm.com>
Signed-off-by: NJassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/mailbox-test.c

@@ -348,7 +348,7 @@ static const struct of_device_id mbox_test_match[] = {
 
 static struct platform_driver mbox_test_driver = {
 	.driver = {
-		.name = "mailbox_sti_test",
+		.name = "mailbox_test",
 		.of_match_table = mbox_test_match,
 	},
 	.probe  = mbox_test_probe,