usb: chipidea: imx: Disable internal 60Mhz clock with ULPI PHY

The internal 60Mhz clock for host2 and host3 are useless in ULPI
phy mode, so we disable it when configuring ULPI PHY node for
those host.

Signed-off-by: Fabien Lahoudere <fabien.lahoudere@collabora.co.uk>
Signed-off-by: Peter Chen <peter.chen@nxp.com>