kernel: Replace ledtrig-netdev with upstream backport

The ledtrig-netdev was added to upstream Linux kernel 4.16, replace our
own version with the patch based on the upstream version.
This will remove the ledtrig-netdev support from kernel 3.18, because I
not want to spend time on backporting it to 3.18. This will make it
easier to use the upstream version with kernel 4.19, by just not
applying this patch.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

target/linux/generic/pending-3.18/831-ledtrig_netdev.patch

@@ -1,21 +0,0 @@
---- a/drivers/leds/trigger/Kconfig
-+++ b/drivers/leds/trigger/Kconfig
-@@ -108,4 +108,11 @@ config LEDS_TRIGGER_CAMERA
- 	  This enables direct flash/torch on/off by the driver, kernel space.
- 	  If unsure, say Y.
- 
-+config LEDS_TRIGGER_NETDEV
-+	tristate "LED Netdev Trigger"
-+	depends on NET && LEDS_TRIGGERS
-+	help
-+	  This allows LEDs to be controlled by network device activity.
-+	  If unsure, say Y.
-+
- endif # LEDS_TRIGGERS
---- a/drivers/leds/Makefile
-+++ b/drivers/leds/Makefile
-@@ -62,3 +62,4 @@ obj-$(CONFIG_LEDS_DAC124S085)		+= leds-d
- 
- # LED Triggers
- obj-$(CONFIG_LEDS_TRIGGERS)		+= trigger/
-+obj-$(CONFIG_LEDS_TRIGGER_NETDEV)	+= ledtrig-netdev.o