usb: chipidea: refine PHY operation

- Delete global_phy due to we can get the phy from phy layer now
- using devm_usb_get_phy to instead of usb_get_phy
- delete the otg_set_peripheral, which should be handled by otg layer

Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>