arcnet/com20020: add LEDS_CLASS dependency

The newly added led trigger support in the com20020-pci driver causes
build errors when CONFIG_LEDS_CLASS is disabled:

drivers/built-in.o: In function `com20020pci_probe':
(.text+0x185dc4): undefined reference to `devm_led_classdev_register'
(.text+0x185dd8): undefined reference to `devm_led_classdev_register'

This adds a Kconfig dependency to prevent the invalid configurations.
Other drivers appear to be split 50:50 between 'select' and 'depends on'
for this symbol, I picked 'depends on' as I could not find a common
policy and it generally causes fewer problems.
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Fixes: 8890624a ("arcnet: com20020-pci: add led trigger support")
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/arcnet/Kconfig

@@ -103,6 +103,7 @@ config ARCNET_RIM_I
 
 config ARCNET_COM20020
 	tristate "ARCnet COM20020 chipset driver"
+	depends on LEDS_CLASS
 	help
 	  This is the driver for the new COM20020 chipset. It supports such
 	  things as promiscuous mode, so packet sniffing is possible, and