stmmac: fix vlan support setup

Moved STMMAC_VLAN_TAG_USED from stmmac.h to common.h header
because it is used within the device and descriptor cores.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/stmmac/common.h b/drivers/net/stmmac/common.h
index 27a05b4..144f76f 100644
--- a/drivers/net/stmmac/common.h
+++ b/drivers/net/stmmac/common.h
@@ -23,6 +23,11 @@
 *******************************************************************************/
 
 #include <linux/netdevice.h>
+#if defined(CONFIG_VLAN_8021Q) || defined(CONFIG_VLAN_8021Q_MODULE)
+#define STMMAC_VLAN_TAG_USED
+#include <linux/if_vlan.h>
+#endif
+
 #include "descs.h"
 
 #undef CHIP_DEBUG_PRINT