net: mdio: Use mb() to be compatible for both ARM and PowerPC

Use mb() instead of sync assembly instruction to be
compatible for both ARM and PowerPC.

Signed-off-by: Alison Wang <alison.wang@freescale.com>

drivers/net/fsl_mdio.c

@@ -19,7 +19,8 @@ void tsec_local_mdio_write(struct tsec_mii_mng __iomem *phyregs, int port_addr,
 
 	out_be32(&phyregs->miimadd, (port_addr << 8) | (regnum & 0x1f));
 	out_be32(&phyregs->miimcon, value);
-	asm("sync");
+	/* Memory barrier */
+	mb();
 
 	while ((in_be32(&phyregs->miimind) & MIIMIND_BUSY) && timeout--)
 		;
@@ -37,11 +38,13 @@ int tsec_local_mdio_read(struct tsec_mii_mng __iomem *phyregs, int port_addr,
 
 	/* Clear the command register, and wait */
 	out_be32(&phyregs->miimcom, 0);
-	asm("sync");
+	/* Memory barrier */
+	mb();
 
 	/* Initiate a read command, and wait */
 	out_be32(&phyregs->miimcom, MIIMCOM_READ_CYCLE);
-	asm("sync");
+	/* Memory barrier */
+	mb();
 
 	/* Wait for the the indication that the read is done */
 	while ((in_be32(&phyregs->miimind) & (MIIMIND_NOTVALID | MIIMIND_BUSY))