net: stm32: add designware mac glue code for stm32

This patch adds glue code required for enabling the designware
mac on stm32f7 devices.

Signed-off-by: Michael Kurz <michi.kurz@gmail.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/drivers/net/designware.c b/drivers/net/designware.c
index f242fc6..e207bc6 100644
--- a/drivers/net/designware.c
+++ b/drivers/net/designware.c
@@ -763,6 +763,7 @@
 	{ .compatible = "allwinner,sun7i-a20-gmac" },
 	{ .compatible = "altr,socfpga-stmmac" },
 	{ .compatible = "amlogic,meson6-dwmac" },
+	{ .compatible = "st,stm32-dwmac" },
 	{ }
 };