usb: renesas_usbhs: enable DVSE interrupt

Commit [1] enabled the possibility of checking the DVST (Device State
Transition) bit of INTSTS0 (Interrupt Status Register 0) and calling
the irq_dev_state() handler if the DVST bit is set. But neither
commit [1] nor commit [2] actually enabled the DVSE (Device State
Transition Interrupt Enable) bit in the INTENB0 (Interrupt Enable
Register 0). As a consequence, irq_dev_state() handler is getting
called as a side effect of other (non-DVSE) interrupts being fired,
which definitely can't be relied upon, if DVST notifications are of
any value.

Why this doesn't hurt is because usbhsg_irq_dev_state() currently
doesn't do much except of a dev_dbg(). Once more work is added to
the handler (e.g. detecting device "Suspended" state and notifying
other USB gadget components about it), enabling DVSE becomes a hard
requirement. Do it in a standalone commit for better visibility and
clear explanation.

[1] commit f1407d5c66 ("usb: renesas_usbhs: Add Renesas USBHS common
   code")
[2] commit 2f98382dcd ("usb: renesas_usbhs: Add Renesas USBHS Gadget")

Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Signed-off-by: Veeraiyan Chidambaram <veeraiyan.chidambaram@in.bosch.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/1568207756-22325-2-git-send-email-external.veeraiyan.c@de.adit-jv.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/renesas_usbhs/mod.c

@@ -338,10 +338,6 @@ void usbhs_irq_callback_update(struct usbhs_priv *priv, struct usbhs_mod *mod)
 	 *	usbhs_interrupt
 	 */
 
-	/*
-	 * it don't enable DVSE (intenb0) here
-	 * but "mod->irq_dev_state" will be called.
-	 */
 	if (info->irq_vbus)
 		intenb0 |= VBSE;
 
@@ -352,6 +348,9 @@ void usbhs_irq_callback_update(struct usbhs_priv *priv, struct usbhs_mod *mod)
 		if (mod->irq_ctrl_stage)
 			intenb0 |= CTRE;
 
+		if (mod->irq_dev_state)
+			intenb0 |= DVSE;
+
 		if (mod->irq_empty && mod->irq_bempsts) {
 			usbhs_write(priv, BEMPENB, mod->irq_bempsts);
 			intenb0 |= BEMPE;