{net,IB}/{rxe,usnic}: Utilize generic mac to eui32 function

This logic seems to be duplicated in (at least) three separate files.
Move it to one place so code can be re-use.

Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index 1aeb25d..2452e64 100644
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h
@@ -103,12 +103,24 @@
 				 u32 addr_flags, bool sllao, bool tokenized,
 				 __u32 valid_lft, u32 prefered_lft);
 
+static inline void addrconf_addr_eui48_base(u8 *eui, const char *const addr)
+{
+	memcpy(eui, addr, 3);
+	eui[3] = 0xFF;
+	eui[4] = 0xFE;
+	memcpy(eui + 5, addr + 3, 3);
+}
+
+static inline void addrconf_addr_eui48(u8 *eui, const char *const addr)
+{
+	addrconf_addr_eui48_base(eui, addr);
+	eui[0] ^= 2;
+}
+
 static inline int addrconf_ifid_eui48(u8 *eui, struct net_device *dev)
 {
 	if (dev->addr_len != ETH_ALEN)
 		return -1;
-	memcpy(eui, dev->dev_addr, 3);
-	memcpy(eui + 5, dev->dev_addr + 3, 3);
 
 	/*
 	 * The zSeries OSA network cards can be shared among various
@@ -123,14 +135,16 @@
 	 * case.  Hence the resulting interface identifier has local
 	 * scope according to RFC2373.
 	 */
+
+	addrconf_addr_eui48_base(eui, dev->dev_addr);
+
 	if (dev->dev_id) {
 		eui[3] = (dev->dev_id >> 8) & 0xFF;
 		eui[4] = dev->dev_id & 0xFF;
 	} else {
-		eui[3] = 0xFF;
-		eui[4] = 0xFE;
 		eui[0] ^= 2;
 	}
+
 	return 0;
 }