dt-bindings: net: microchip: Allow nvmem-cell usage

MAC address can be provided by a nvmem-cell, thus allow referencing a
source for the address. Fixes the warning:
arch/arm/boot/dts/nxp/imx/imx6q-mba6a.dtb: ethernet@1: 'nvmem-cell-names',
 'nvmem-cells' do not match any of the regexes: 'pinctrl-[0-9]+'
 From schema: Documentation/devicetree/bindings/net/microchip,lan95xx.yaml

Signed-off-by: Alexander Stein <[email protected]>
Acked-by: Conor Dooley <[email protected]>
Reviewed-by: Rob Herring <[email protected]>
Signed-off-by: Daniel Lezcano <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: tq-steina

Documentation/devicetree/bindings/net/microchip,lan95xx.yaml

@@ -44,6 +44,8 @@ properties:
 
   local-mac-address: true
   mac-address: true
+  nvmem-cells: true
+  nvmem-cell-names: true
 
 required:
   - compatible