usb: musb: core: call init and shutdown for the usb phy

The phy's init routine must be called before it can be used. Do so in
musb_init_controller and the matching shutdown in musb_remove.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>