mailbox: stm32-ipcc: remove useless device_init_wakeup call

If the "wakeup-source" property does not exist there is no need to call
device_init_wakeup("false") at probe.

Signed-off-by: Fabien Dessenne <[e-mail]>
Signed-off-by: Jassi Brar <[e-mail]>

drivers/mailbox/stm32-ipcc.c

···
 			dev_err(dev, "Failed to set wake up irq\n");
 			goto err_init_wkp;
 		}
-	} else {
-		device_init_wakeup(dev, false);
 	}
 
 	/* mailbox controller */