gpio: mpc8xxx: add ls1088a platform gpio node DT binding description

ls1088a and ls1028a platform share common gpio node.

Signed-off-by: Song Hui <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

Documentation/devicetree/bindings/gpio/gpio-mpc8xxx.txt

···
 - compatible : Should be "fsl,<soc>-gpio"
   The following <soc>s are known to be supported:
 	mpc5121, mpc5125, mpc8349, mpc8572, mpc8610, pq3, qoriq,
-	ls1021a, ls1043a, ls2080a, ls1028a.
+	ls1021a, ls1043a, ls2080a, ls1028a, ls1088a.
 - reg : Address and length of the register set for the device
 - interrupts : Should be the port interrupt shared by all 32 pins.
 - #gpio-cells : Should be two.  The first cell is the pin number and
···
 };
 
 
-Example of gpio-controller node for a ls1028a SoC:
+Example of gpio-controller node for a ls1028a/ls1088a SoC:
 
 gpio1: gpio@2300000 {
-	compatible = "fsl,ls1028a-gpio","fsl,qoriq-gpio";
+	compatible = "fsl,ls1028a-gpio", "fsl,ls1088a-gpio", "fsl,qoriq-gpio";
 	reg = <0x0 0x2300000 0x0 0x10000>;
 	interrupts = <GIC_SPI 36 IRQ_TYPE_LEVEL_HIGH>;
 	gpio-controller;