usb: musb: omap2430: make sure clocks are enabled when running mailbox

on early initialization we could fall into
a situation where the mailbox is called before
MUSB's clocks are running, in order to avoid
that, make sure mailbox is always wrapped with
pm_runtime calls.
Reported-by: NStefan Roese <sr@denx.de>
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/usb/musb/omap2430.c

@@ -316,7 +316,13 @@ static void omap_musb_mailbox_work(struct work_struct *mailbox_work)
 {
 	struct omap2430_glue *glue = container_of(mailbox_work,
 				struct omap2430_glue, omap_musb_mailbox_work);
+	struct musb *musb = glue_to_musb(glue);
+	struct device *dev = musb->controller;
+
+	pm_runtime_get_sync(dev);
 	omap_musb_set_mailbox(glue);
+	pm_runtime_mark_last_busy(dev);
+	pm_runtime_put_autosuspend(dev);
 }
 
 static irqreturn_t omap2430_musb_interrupt(int irq, void *__hci)