treewide: use DEFAULT := n to disable non-broken devices

This uses DEFAULT := n on a bunch of devices that previously were
"disabled" by commenting out TARGET_DEVICES. This will allow to
build them without having to modify the code, but they will not
be selected for default build or buildbots.

The change is applied to all devices that are not "broken", but suffer
from image site limitations or similar, or have been added in the past
but never confirmed to run on the device properly:

at91: at91-q5xr5:
  kernel image too big
  31aeae0774 ("at91: do not build image for at91-q5xr5")

bcm47xx: asus-rt-ac66u:
  disabled since it was added in 2015
  69aefc771f ("brcm47xx: build images for Asus devices")

bcm47xx: netgear-wndr3400-vcna, netgear-wnr3500u, netgear-wnr3500-v2-vc
  added disabled in 2012, but never confirmed to work on devices
  5dec9dd3b2 ("brcm47xx: add code to generate images for some netgear
    devices")

bcm53xx: netgear-r8500
  added disabled: "start working on Netgear R8500"
  3b76c7cf0b ("bcm53xx: start working on Netgear R8500")

Signed-off-by: Petr Štetiar <ynezz@true.cz>
[limit to subset of devices, adjust commit message/title]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/at91/image/sam9x.mk

@@ -173,8 +173,9 @@ define Device/at91-q5xr5
   DEVICE_VENDOR := Exegin
   DEVICE_MODEL := Q5XR5
   KERNEL_SIZE := 2048k
+  DEFAULT := n
 endef
-#TARGET_DEVICES += at91-q5xr5
+TARGET_DEVICES += at91-q5xr5
 
 define Device/wb45n
   $(Device/evaluation-fit)

target/linux/bcm47xx/image/mips74k.mk

@@ -15,8 +15,9 @@ define Device/asus-rt-ac66u
   DEVICE_PACKAGES := kmod-b43 $(USB2_PACKAGES)
   $(Device/asus)
   PRODUCTID := RT-AC66U
+  DEFAULT := n
 endef
-#  TARGET_DEVICES += asus-rt-ac66u
+TARGET_DEVICES += asus-rt-ac66u
 
 define Device/asus-rt-n10
   DEVICE_MODEL := RT-N10
@@ -399,8 +400,9 @@ define Device/netgear-wndr3400-vcna
   $(Device/netgear)
   NETGEAR_BOARD_ID := U12H155T01_NETGEAR
   NETGEAR_REGION := 2
+  DEFAULT := n
 endef
-#  TARGET_DEVICES += netgear-wndr3400-vcna
+TARGET_DEVICES += netgear-wndr3400-vcna
 
 define Device/netgear-wndr4000
   DEVICE_MODEL := WNDR4000
@@ -467,8 +469,9 @@ define Device/netgear-wnr3500u
   $(Device/netgear)
   NETGEAR_BOARD_ID := U12H136T00_NETGEAR
   NETGEAR_REGION := 2
+  DEFAULT := n
 endef
-#  TARGET_DEVICES += netgear-wnr3500u
+TARGET_DEVICES += netgear-wnr3500u
 
 define Device/netgear-wnr3500-v2
   DEVICE_MODEL := WNR3500
@@ -487,7 +490,8 @@ define Device/netgear-wnr3500-v2-vc
   $(Device/netgear)
   NETGEAR_BOARD_ID := U12H127T70_NETGEAR
   NETGEAR_REGION := 2
+  DEFAULT := n
 endef
-#  TARGET_DEVICES += netgear-wnr3500-v2-vc
+TARGET_DEVICES += netgear-wnr3500-v2-vc
 
 TARGET_DEVICES += standard standard-noloader-nodictionarylzma

target/linux/bcm53xx/image/Makefile

@@ -370,8 +370,9 @@ define Device/netgear-r8500
   DEVICE_PACKAGES := $(BRCMFMAC_4366B1) $(USB3_PACKAGES)
   $(Device/netgear)
   NETGEAR_BOARD_ID := U12H334T00_NETGEAR
+  DEFAULT := n
 endef
-# TARGET_DEVICES += netgear-r8500
+TARGET_DEVICES += netgear-r8500
 
 define Device/smartrg-sr400ac
   DEVICE_VENDOR := SmartRG