usb: host: ohci-at91: add support to enter suspend using SMC

usb: host: ohci-at91: add support to enter suspend using SMC

When Linux is running under OP-TEE, the SFR is set as secured and thus
the AT91_OHCIICR_USB_SUSPEND register isn't accessible. Add a SMC to
do the appropriate call to suspend the controller.
The SMC id is fetched from the device-tree property
"microchip,suspend-smc-id". if present, then the syscon regmap is not
used to enter suspend and a SMC is issued.

Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Clément Léger <clement.leger@bootlin.com>
Link: https://lore.kernel.org/r/20220607133454.727063-1-clement.leger@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>