phy: rockchip-usb: expose the phy-internal PLLs

The USB phys on Rockchip SoCs contain their own internal PLLs to create
the 480MHz needed. Additionally this PLL output is also fed back into the
core clock-controller as possible source for clocks like the GPU or others.

Until now this was modelled incorrectly with a "virtual" factor clock in
the clock controller. The one big caveat is that if we turn off the usb phy
via the siddq signal, all analog components get turned off, including the
PLLs. It is therefore possible that a source clock gets disabled without
the clock driver ever knowing, possibly making the system hang.

Therefore register the phy-plls as real clocks that the clock driver can
then reference again normally, making the clock hirarchy finally reflect
the actual hardware.

The phy-ops get converted to simply turning that new clock on and off
which in turn controls the siddq signal of the phy.

Through this the driver gains handling for platform-specific data, to
handle the phy->clock name association.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>