ARM: dts: arria10: add board compatible for Mercury AA1

The Enclustra Mercury AA1 is a module with Arria 10, so it needs its own
compatible.
Signed-off-by: NKrzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: NDinh Nguyen <dinguyen@kernel.org>

arch/arm/boot/dts/socfpga_arria10_mercury_aa1.dts

@@ -6,7 +6,7 @@
 / {
 
 	model = "Enclustra Mercury AA1";
-	compatible = "altr,socfpga-arria10", "altr,socfpga";
+	compatible = "enclustra,mercury-aa1", "altr,socfpga-arria10", "altr,socfpga";
 
 	aliases {
 		ethernet0 = &gmac0;