USB: otg: twl4030: add support for notifier

it's expected that the transceiver driver will
initialize and call the notifier chain when
necessary. Implement that for twl4030-usb driver.

Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>