ARM: at91: rm9200: fix usb device clock id

Referring to the datasheet the index 2 is the MCKUDP. When enabled, it
"Enables the automatic disable of the Master Clock of the USB Device
Port when a suspend condition occurs". We fix the index to the real UDP
id which "Enables the 48 MHz clock of the USB Device Port".

Cc: nicolas.ferre@microchip.com
Cc: ludovic.desroches@microchip.com
Cc: alexandre.belloni@bootlin.com
Cc: mturquette@baylibre.com
Cc: sboyd@kernel.org
Cc: claudiu.beznea@microchip.com
Cc: linux-clk@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: kernel@pengutronix.de
Fixes: 02ff48e4 ("clk: at91: add at91rm9200 pmc driver")
Fixes: 0e0e528d ("ARM: dts: at91: rm9200: switch to new clock bindings")
Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20221114185923.1023249-2-m.grzeschik@pengutronix.de