arm: omap: usb: allow for external transceiver control

In PHY mode, ehci/ohci can have an external transceiver.
Eg: USB3333 - which needs 19.2Mhz input clock supplied by omap.

Pass clk data to driver so that as part of usb bus suspend
this clock can be controlled for OMAP to enter low power state.

Change-Id: I6ac0ee1791b5f040f1913fe888d24cf411398965