ARM: dts: socfpga: align interrupt controller node name with dtschema

Fixes dtbs_check warnings like:

  $nodename:0: 'intc@fffed000' does not match '^interrupt-controller(@[0-9a-f,]+)*$'

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Dinh Nguyen <dinguyen@kernel.org>
Link: https://lore.kernel.org/r/20220317115705.450427-2-krzysztof.kozlowski@canonical.com