dt-bindings: net: snps,dwmac: add dwmac 3.40a IP version

dwmac 3.40a is an old ip version that can be found on SPEAr3xx soc.
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -21,6 +21,7 @@ select:
       contains:
         enum:
           - snps,dwmac
+          - snps,dwmac-3.40a
           - snps,dwmac-3.50a
           - snps,dwmac-3.610
           - snps,dwmac-3.70a
@@ -76,6 +77,7 @@ properties:
         - rockchip,rk3399-gmac
         - rockchip,rv1108-gmac
         - snps,dwmac
+        - snps,dwmac-3.40a
         - snps,dwmac-3.50a
         - snps,dwmac-3.610
         - snps,dwmac-3.70a