usb: chipidea: add support to the generic PHY framework

This patch adds support of the PHY framework for ChipIdea drivers.
Changes are done in both the ChipIdea common code and in the drivers
accessing the PHY. This is done by adding a new PHY member in
ChipIdea's structures and by taking care of it in the code.

Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Acked-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>