phy: usb: Turn off phy when port is in suspend

The COMMONONN bit turns off the PHY when the host controller puts it
into suspend state. This can happen during the following...
- Nothing is connected to the port
- The host controller goes into low power mode whatever due to auto
  suspend or system suspend.

With COMMONONN we also must unset U2_FREECLK_EXISTS since the UTMI
clock is fed by the PHY.

With these changes we see a power savings of ~12mW when port is in
suspend.

Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Justin Chen <justin.chen@broadcom.com>
Link: https://lore.kernel.org/r/1686859578-45242-2-git-send-email-justin.chen@broadcom.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>