usb: otg: support for multiple transceivers by a single controller

Add a linked list for keeping multiple PHY instances with different
types so that we can have separate USB2 and USB3 PHYs on one single
board. _get_phy_ has been changed so that the controller gets
the transceiver by type. _remove_phy_ has been added to let the phy
be removed from the phy list.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/musb/am35x.c b/drivers/usb/musb/am35x.c
index a75989b..4a8cbf0 100644
--- a/drivers/usb/musb/am35x.c
+++ b/drivers/usb/musb/am35x.c
@@ -364,7 +364,7 @@
 		return -ENODEV;
 
 	usb_nop_xceiv_register();
-	musb->xceiv = usb_get_phy();
+	musb->xceiv = usb_get_phy(USB_PHY_TYPE_USB2);
 	if (!musb->xceiv)
 		return -ENODEV;