drivers: soc: atmel: Avoid calling at91_soc_init on non AT91 SoCs

Since at91_soc_init is called unconditionally from atmel_soc_device_init,
we get the following warning on all non AT91 SoCs:
	" AT91: Could not find identification node"

Fix the same by filtering with allowed AT91 SoC list.

Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Ludovic Desroches <ludovic.desroches@microchip.com>
Cc: stable@vger.kernel.org #4.12+
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201211135846.1334322-1-sudeep.holla@arm.com


Signed-off-by: Arnd Bergmann <arnd@arndb.de>