ARM: dts: at91: use generic name for reset controller

Use generic name for reset controller of AT91 devices to comply with
DT specifications.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220610092414.1816571-2-claudiu.beznea@microchip.com