phy: rockchip-usb: fix clock get-put mismatch

Currently the phy driver only gets the optional clock reference but
never puts it again, neither during error handling nor on remove.
Fix that by moving the clk_put to a devm-action that gets called at
the right time when all other devm actions are done.

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>