usb: ehci-orion: add S2RAM support

Add suspend/resume callbacks to reset the host controller properly
during S2RAM operation.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>