devicetree: bindings: improve description for GPIO assisted NAND flash

Expand the description of the 'gpios' property in the GPIO assisted
NAND flash binding, to explicitly list the required GPIO pin references
and their order.

Update the example section to individually bracket the GPIO references,
and capitalize the signal names for improved readability.

Signed-off-by: Gerhard Sittig <[e-mail]>
Signed-off-by: Brian Norris <[e-mail]>

Documentation/devicetree/bindings/mtd/gpio-control-nand.txt

···
   are made in native endianness.
 - #address-cells, #size-cells : Must be present if the device has sub-nodes
   representing partitions.
-- gpios : specifies the gpio pins to control the NAND device.  nwp is an
-  optional gpio and may be set to 0 if not present.
+- gpios : Specifies the GPIO pins to control the NAND device.  The order of
+  GPIO references is:  RDY, nCE, ALE, CLE, and an optional nWP.
 
 Optional properties:
 - bank-width : Width (in bytes) of the device.  If not present, the width
···
 	reg = <1 0x0000 0x2>;
 	#address-cells = <1>;
 	#size-cells = <1>;
-	gpios = <&banka 1 0	/* rdy */
-		 &banka 2 0 	/* nce */
-		 &banka 3 0 	/* ale */
-		 &banka 4 0 	/* cle */
-		 0		/* nwp */>;
+	gpios = <&banka 1 0>,	/* RDY */
+		<&banka 2 0>, 	/* nCE */
+		<&banka 3 0>, 	/* ALE */
+		<&banka 4 0>, 	/* CLE */
+		<0>;		/* nWP */
 
 	partition@0 {
 	...