igb: Fix -Wunused-const-variable warning

If CONFIG_IGB_HWMON is n, gcc warns:

drivers/net/ethernet/intel/igb/e1000_82575.c:2765:17:
 warning: ‘e1000_emc_therm_limit’ defined but not used [-Wunused-const-variable=]
 static const u8 e1000_emc_therm_limit[4] = {
                 ^~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/intel/igb/e1000_82575.c:2759:17:
 warning: ‘e1000_emc_temp_data’ defined but not used [-Wunused-const-variable=]
 static const u8 e1000_emc_temp_data[4] = {
                 ^~~~~~~~~~~~~~~~~~~

Move it into #ifdef block to fix this.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/intel/igb/e1000_82575.c

@@ -2756,6 +2756,7 @@ s32 igb_get_eee_status_i354(struct e1000_hw *hw, bool *status)
 	return ret_val;
 }
 
+#ifdef CONFIG_IGB_HWMON
 static const u8 e1000_emc_temp_data[4] = {
 	E1000_EMC_INTERNAL_DATA,
 	E1000_EMC_DIODE1_DATA,
@@ -2769,7 +2770,6 @@ static const u8 e1000_emc_therm_limit[4] = {
 	E1000_EMC_DIODE3_THERM_LIMIT
 };
 
-#ifdef CONFIG_IGB_HWMON
 /**
  *  igb_get_thermal_sensor_data_generic - Gathers thermal sensor data
  *  @hw: pointer to hardware structure