When suspending usb bus, phy driver may disable controller power.
In this case, registers need to be saved on suspend and restored
on resume.
Acked-by: NJohn Youn <johnyoun@synopsys.com>
Signed-off-by: NGregory Herrero <gregory.herrero@intel.com>
Signed-off-by: NFelipe Balbi <balbi@ti.com>