devicetree: Add JZ4760/JZ4775 to Ingenic SoC UART binding

Add these variants of the UART as compatible strings
Signed-off-by: NMatt Redfearn <matt.redfearn@imgtec.com>

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Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/ingenic,uart.txt

 * Ingenic SoC UART
 
 Required properties:
-- compatible : "ingenic,jz4740-uart" or "ingenic,jz4780-uart"
+- compatible : "ingenic,jz4740-uart", "ingenic,jz4760-uart",
+	"ingenic,jz4775-uart" or "ingenic,jz4780-uart"
 - reg : offset and length of the register set for the device.
 - interrupts : should contain uart interrupt.
 - clocks : phandles to the module & baud clocks.