usb: gadget: udc: atmel: Also get regmap for at91sam9x5-pmc

The "atmel,at91sam9g45-udc" compatible UDC is also used on at91sam9x5 so it
is also necessary to try to get the syscon for at91sam9x5-pmc.

Fixes: 4747639f ("usb: gadget: atmel: access the PMC using regmap")
Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>