ARM: dts: socfpga: Add enclustra PE1 devicetree

The enclustra PE1 is a baseboard from enclustra GmbH for the enclustra
Mercury AA1+ SOM.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>