USB: dwc3: refactor phy handling

Refactor the PHY handling using four new helpers to initialise,
deinitialise, power on and power off all the PHYs.

Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20230404072524.19014-10-johan+linaro@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>