net: stmmac:sti: Add STi SOC glue driver.

STi series SOCs have a glue layer on top of the synopsis gmac IP, this
glue layer needs to be configured before the gmac driver starts using
the IP.

This patch adds a support to this glue layer which is configured via
stmmac setup, init, exit callbacks.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index d9af26e..f9e60d7 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -133,6 +133,9 @@
 #ifdef CONFIG_DWMAC_SUNXI
 extern const struct stmmac_of_data sun7i_gmac_data;
 #endif
+#ifdef CONFIG_DWMAC_STI
+extern const struct stmmac_of_data sti_gmac_data;
+#endif
 extern struct platform_driver stmmac_pltfr_driver;
 static inline int stmmac_register_platform(void)
 {