lantiq: fix build of squashfs images

This patch fixes build of squashfs image on lantiq. Currently the FEATURE
variable is overwritten by the subtarget.

Fixes: FS#3480
Fixes: f1c6523376 ("lantiq: clean up target/subtarget features")

Signed-off-by: Aleksander Jan Bajkowski <A.Bajkowski@stud.elka.pw.edu.pl>
[reformat Fixes:]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/lantiq/ase/target.mk

@@ -7,7 +7,7 @@
 ARCH:=mips
 SUBTARGET:=ase
 BOARDNAME:=Amazon-SE
-FEATURES:=atm mips16 small_flash
+FEATURES+=atm mips16 small_flash
 CPU_TYPE:=mips32
 
 DEFAULT_PACKAGES+=kmod-leds-gpio kmod-gpio-button-hotplug \

target/linux/lantiq/falcon/target.mk

@@ -1,7 +1,7 @@
 ARCH:=mips
 SUBTARGET:=falcon
 BOARDNAME:=Falcon
-FEATURES:=nand
+FEATURES+=nand
 CPU_TYPE:=24kc
 
 DEFAULT_PACKAGES+= kmod-leds-gpio \

target/linux/lantiq/xrx200/target.mk

@@ -1,7 +1,7 @@
 ARCH:=mips
 SUBTARGET:=xrx200
 BOARDNAME:=XRX200
-FEATURES:=atm nand ramdisk
+FEATURES+=atm nand ramdisk
 CPU_TYPE:=24kc
 
 DEFAULT_PACKAGES+=kmod-leds-gpio \

target/linux/lantiq/xway/target.mk

@@ -1,7 +1,7 @@
 ARCH:=mips
 SUBTARGET:=xway
 BOARDNAME:=XWAY
-FEATURES:=atm nand ramdisk
+FEATURES+=atm nand ramdisk
 CPU_TYPE:=24kc
 
 DEFAULT_PACKAGES+=kmod-leds-gpio kmod-gpio-button-hotplug swconfig

target/linux/lantiq/xway_legacy/target.mk

@@ -1,7 +1,7 @@
 ARCH:=mips
 SUBTARGET:=xway_legacy
 BOARDNAME:=XWAY Legacy
-FEATURES:=atm ramdisk small_flash
+FEATURES+=atm ramdisk small_flash
 CPU_TYPE:=24kc
 
 DEFAULT_PACKAGES+=kmod-leds-gpio kmod-gpio-button-hotplug swconfig