dt-bindings: net: dsa: microchip: Make pinctrl 'reset' optional

Commit e469b87e0f ("dt-bindings: net: dsa: microchip: Add strap
description to set SPI mode") required both 'default' and 'reset' pinctrl
states for all compatible devices. However, this requirement should be only
applicable to KSZ8463.

Make the 'reset' pinctrl state optional for all other Microchip DSA
devices while keeping it mandatory for KSZ8463.

Fix below CHECK_DTBS warnings:
  arch/arm64/boot/dts/freescale/imx8mp-skov-basic.dtb: switch@5f (microchip,ksz9893): pinctrl-names: ['default'] is too short
	from schema $id: http://devicetree.org/schemas/net/dsa/microchip,ksz.yaml#

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Marco Felsch <m.felsch@pengutronix.de>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260106143620.126212-1-Frank.Li@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml

@@ -40,6 +40,7 @@ properties:
       - const: reset
         description:
           Used during reset for strap configuration.
+    minItems: 1
 
   reset-gpios:
     description:
@@ -153,6 +154,8 @@ allOf:
             const: microchip,ksz8463
     then:
       properties:
+        pinctrl-names:
+          minItems: 2
         straps-rxd-gpios:
           description:
             RXD0 and RXD1 pins, used to select SPI as bus interface.