usb: gadget: udc: atmel: handle at91sam9rl PMC

The at91sam9rl PMC is not quite the same as the at91sam9g45 one and now has
its own compatible string. Add support for that.

Fixes: 217bace8e548 ("ARM: dts: fix PMC compatible")
Acked-by: Cristian Birsan <cristian.birsan@microchip.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>