dt-bindings: memory: jz4780: Add compatible string for JZ4740 SoC

Add a compatible string to support the memory controller built into the
JZ4740 SoC from Ingenic.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Boris Brezillon <bbrezillon@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Paul Burton <paul.burton@mips.com>

Documentation/devicetree/bindings/memory-controllers/ingenic,jz4780-nemc.txt

@@ -5,6 +5,7 @@ controller in Ingenic JZ4780
 
 Required properties:
 - compatible: Should be set to one of:
+    "ingenic,jz4740-nemc" (JZ4740)
     "ingenic,jz4780-nemc" (JZ4780)
 - reg: Should specify the NEMC controller registers location and length.
 - clocks: Clock for the NEMC controller.