DaVinci EMAC: Fix davinci_eth_gigabit_enable

Enabling the gigabit was overwriting the
previous configuration by setting up only GIGAFORCE and
GIG bits of MAC control register.
Modified to retain previous configuration while
gigabit enabling.

Signed-off-by: Prakash PM <prakash.pm@ti.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>

drivers/net/davinci_emac.c

@@ -322,9 +322,10 @@ static void  __attribute__((unused)) davinci_eth_gigabit_enable(void)
 			 * Check if link detected is giga-bit
 			 * If Gigabit mode detected, enable gigbit in MAC
 			 */
-			writel(EMAC_MACCONTROL_GIGFORCE |
-			       EMAC_MACCONTROL_GIGABIT_ENABLE,
-			       &adap_emac->MACCONTROL);
+			writel(readl(&adap_emac->MACCONTROL) |
+				EMAC_MACCONTROL_GIGFORCE |
+				EMAC_MACCONTROL_GIGABIT_ENABLE,
+				&adap_emac->MACCONTROL);
 		}
 	}
 }