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

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 <krzysztof.kozlowski@linaro.org>
Acked-by: Matthew Gerlach <matthew.gerlach@altera.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20250902154051.263156-3-krzysztof.kozlowski@linaro.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>