ARM: rockchip: add support holding 24Mhz osc during suspend

If we want to wake up system via usb, the 24Mhz osc could not be
disabled during suspend, read the usb phy SIDDQ bit to decide whether
to switch to 32khz clock-in.

Signed-off-by: Chris Zhong <zyw@rock-chips.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>