usb: musb: ensure in peripheral mode when checking session

The change ensures otg is not in a A- state when checking for VBUS in
peripheral mode.

musb_start() where VBUS checking is in can be called in many situations.
One example is in babble recovery routine, in which otg is transitioning
from A-HOST to A-WAIT-BCON, but VBUS discharge takes time, so
musb->is_active could be set to 1 due to this improper checking, then it
causes musb_bus_suspend() failed which leads to warning log message
flooding.

Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_core.c

@@ -1051,6 +1051,7 @@ void musb_start(struct musb *musb)
 	 * (c) peripheral initiates, using SRP
 	 */
 	if (musb->port_mode != MUSB_PORT_MODE_HOST &&
+			musb->xceiv->otg->state != OTG_STATE_A_WAIT_BCON &&
 			(devctl & MUSB_DEVCTL_VBUS) == MUSB_DEVCTL_VBUS) {
 		musb->is_active = 1;
 	} else {