be2net: make hwmon interface optional

The hwmon interface in the be2net driver causes a link error when
be2net is built-in while the hwmon subsystem is a loadable module:

drivers/built-in.o: In function `be_probe':
drivers/net/ethernet/emulex/benet/be_main.c:5761: undefined reference to `devm_hwmon_device_register_with_groups'

This adds a new Kconfig symbol, following the example of multiple
other drivers that have the same problem. The new CONFIG_BE2NET_HWMON
will not be available when (BE2NET=y && HWMON=m) to avoid this
problem.

We have to also mark be_hwmon_show_temp as 'static' to ensure the
compiler can optimize out all the unused code.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 29e9122b ("be2net: Export board temperature using hwmon-sysfs interface.")
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/emulex/benet/Kconfig

@@ -5,6 +5,15 @@ config BE2NET
 	  This driver implements the NIC functionality for ServerEngines'
 	  10Gbps network adapter - BladeEngine.
 
+config BE2NET_HWMON
+	bool "HWMON support for be2net driver"
+	depends on BE2NET && HWMON
+	depends on !(BE2NET=y && HWMON=m)
+	default y
+	---help---
+	  Say Y here if you want to expose thermal sensor data on
+	  be2net network adapter.
+
 config BE2NET_VXLAN
         bool "VXLAN offload support on be2net driver"
         default y

drivers/net/ethernet/emulex/benet/be_main.c

@@ -5612,9 +5612,9 @@ static void be_remove(struct pci_dev *pdev)
 	free_netdev(adapter->netdev);
 }
 
-ssize_t be_hwmon_show_temp(struct device *dev,
-			   struct device_attribute *dev_attr,
-			   char *buf)
+static ssize_t be_hwmon_show_temp(struct device *dev,
+				  struct device_attribute *dev_attr,
+				  char *buf)
 {
 	struct be_adapter *adapter = dev_get_drvdata(dev);
 
@@ -5756,7 +5756,7 @@ static int be_probe(struct pci_dev *pdev, const struct pci_device_id *pdev_id)
 	be_schedule_err_detection(adapter);
 
 	/* On Die temperature not supported for VF. */
-	if (be_physfn(adapter)) {
+	if (be_physfn(adapter) && IS_ENABLED(CONFIG_BE2NET_HWMON)) {
 		adapter->hwmon_info.hwmon_dev =
 			devm_hwmon_device_register_with_groups(&pdev->dev,
 							       DRV_NAME,