dt-bindings: net: altr,socfpga-stmmac: Constrain interrupts

STMMAC on SoCFPGA uses exactly one interrupt in in-kernel DTS and common
snps,dwmac.yaml binding is flexible, so define precise constraint for
this device.

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Acked-by: Matthew Gerlach <[e-mail]>
Acked-by: Rob Herring (Arm) <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

Documentation/devicetree/bindings/net/altr,socfpga-stmmac.yaml

···
       - const: stmmaceth
       - const: ptp_ref
 
+  interrupts:
+    maxItems: 1
+
+  interrupt-names:
+    items:
+      - const: macirq
+
   iommus:
     minItems: 1
     maxItems: 2