phy: rockchip-inno-usb2: add support for otg-mux interrupt

The otg-id/otg-bvalid/linestate interrupts are multiplexed together
in otg-port on some Rockchip SoC (e.g RV1108), this patch add support
for it.

Signed-off-by: Frank Wang <frank.wang@rock-chips.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>