Snapshot not available for certain supported devices recently

http://phase1.builds.lede-project.org/builders/ar71xx%2Fgeneric/builds/516/steps/images/logs/stdio

It appears that the kernel partition for the Belkin F9K1115 v2 is limited to 1408 KB, which is no longer enough for kernel >= 4.9 (currently 1465.3 KB are required, but this will grow a bit more for kernel 4.14; this was apparently 1239.94 kB for kernel 4.4 in lede-17.01). Several other devices with these issues were able to lift this restriction by slightly changing the mtd partitioning. If similar approaches are possible for the F9K1115 depends on the partition order, how the bootloader accesses the kernel and if the OEM firmware updater accepts a different split between kernel and rootfs (for the factory images) - and it will obviously need experimenting and confirmation (plus a pull request) by a user of this device.