dt-bindings: net: snps,dwmac: Update interrupt-names

As commit fc191af1 ("net: stmmac: platform: Fix misleading
interrupt error msg") noted, not every stmmac based platform
makes use of the 'eth_wake_irq' or 'eth_lpi' interrupts.

So, update the 'interrupt-names' inside 'snps,dwmac' YAML
bindings to reflect the same.
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bhupesh Sharma <bhupesh.sharma@linaro.org>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Tested-by: Brian Masney <bmasney@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Documentation/devicetree/bindings/net/snps,dwmac.yaml

@@ -105,7 +105,7 @@ properties:
     minItems: 1
     items:
       - const: macirq
-      - const: eth_wake_irq
+      - enum: [eth_wake_irq, eth_lpi]
       - const: eth_lpi
 
   clocks: