FEC: Replace magic contants

Replace the magic contant 1 << 24 with properly defined bits.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Joe Hershberger <joe.hershberger@ni.com>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Otavio Salvador <otavio@ossystems.com.br>
Cc: Stefano Babic <sbabic@denx.de>
diff --git a/drivers/net/fec_mxc.c b/drivers/net/fec_mxc.c
index 6ede464..3e232c7 100644
--- a/drivers/net/fec_mxc.c
+++ b/drivers/net/fec_mxc.c
@@ -256,7 +256,7 @@
 
 static int fec_rx_task_enable(struct fec_priv *fec)
 {
-	writel(1 << 24, &fec->eth->r_des_active);
+	writel(FEC_R_DES_ACTIVE_RDAR, &fec->eth->r_des_active);
 	return 0;
 }
 
@@ -267,7 +267,7 @@
 
 static int fec_tx_task_enable(struct fec_priv *fec)
 {
-	writel(1 << 24, &fec->eth->x_des_active);
+	writel(FEC_X_DES_ACTIVE_TDAR, &fec->eth->x_des_active);
 	return 0;
 }
 
@@ -769,7 +769,7 @@
 	 * barrier here.
 	 */
 	while (--timeout) {
-		if (!(readl(&fec->eth->x_des_active) & (1 << 24)))
+		if (!(readl(&fec->eth->x_des_active) & FEC_X_DES_ACTIVE_TDAR))
 			break;
 	}