phy: rockchip-inno-usb2: Implement clock operations for usb2phy clock

This clock doesn't seem needed but appears in a phandle list used by
ehci-generic.c to bulk enable it. The phandle list comes from linux,
where it is needed for suspend/resume to work [1].

My tests give the same results with or without this patch, but Marek
Vasut found it weird to declare an empty clk_ops [2].

So I adapted the code from linux 6.1-rc8 so that it hopefully works
if it ever has some user. For now, without real use, it seems to
at least not give any errors when called.

Link: [1] https://lkml.kernel.org/lkml/1731551.Q6cHK6n5ZM@phil/T/
      [2] https://patchwork.ozlabs.org/project/uboot/patch/Y5IWpjYLB4aXMy9o@localhost/



Cc: Simon Glass <sjg@chromium.org>
Cc: Philipp Tomsich <philipp.tomsich@vrull.eu>
Cc: Kever Yang <kever.yang@rock-chips.com>
Cc: Lukasz Majewski <lukma@denx.de>
Cc: Sean Anderson <seanga2@gmail.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Christoph Fritz <chf.fritz@googlemail.com>
Cc: Jagan Teki <jagan@amarulasolutions.com>

Signed-off-by: Xavier Drudis Ferran <xdrudis@tinet.cat>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com> # rk3399, rk3328, rv1126