generic: force per-device RootFS

All targets now use OpenWrt device abstraction. Thus, all targets now
can be built using a per-device RootFS.

Signed-off-by: David Bauer <mail@david-bauer.net>

targets/generic

@@ -51,8 +51,8 @@ config('KERNEL_IPV6_MROUTE', false)
 
 config('COLLECT_KERNEL_DEBUG', true)
 
-try_config('TARGET_MULTI_PROFILE', true)
-try_config('TARGET_PER_DEVICE_ROOTFS', true)
+config('TARGET_MULTI_PROFILE', true)
+config('TARGET_PER_DEVICE_ROOTFS', true)
 
 config('GLUON_MULTIDOMAIN', istrue(env.GLUON_MULTIDOMAIN))