tg3: Add the ability to conditionally build w/ HWMON

Introduce a Kconfig option: CONFIG_TIGON3_HWMON which allows to build
in/out support for thermal sensors reported by Tigon3 NICs.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/broadcom/Kconfig b/drivers/net/ethernet/broadcom/Kconfig
index 940fb24..9641380 100644
--- a/drivers/net/ethernet/broadcom/Kconfig
+++ b/drivers/net/ethernet/broadcom/Kconfig
@@ -109,7 +109,6 @@
 	tristate "Broadcom Tigon3 support"
 	depends on PCI
 	select PHYLIB
-	select HWMON
 	imply PTP_1588_CLOCK
 	---help---
 	  This driver supports Broadcom Tigon3 based gigabit Ethernet cards.
@@ -117,6 +116,13 @@
 	  To compile this driver as a module, choose M here: the module
 	  will be called tg3.  This is recommended.
 
+config TIGON3_HWMON
+	bool "Broadcom Tigon3 HWMON support"
+	default y
+	depends on TIGON3 && HWMON && !(TIGON3=y && HWMON=m)
+	---help---
+	  Say Y if you want to expose the thermal sensor on Tigon3 devices.
+
 config BNX2X
 	tristate "Broadcom NetXtremeII 10Gb support"
 	depends on PCI