usb: musb: omap: make use of the new PHY lib APIs

New PHY lib APIs like usb_add_phy_dev() and devm_usb_get_phy_dev() are
used in MUSB (OMAP), in order to make use of the binding information
provided in the board file (of OMAP platforms).

All the platforms should be modified similar to this to add and get the
PHY.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>