usb: otg: utils: rename function name in OTG utils

_transceiver() in otg.c is replaced with _phy. usb_set_transceiver is
replaced with usb_add_phy to make it similar to other usb standard
function names like usb_add_hcd.

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